• Applied Chemistry for Engineering
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• v.19 no.4
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• pp.427-431
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• 2008

The rigid polyurethane foams (PUF) were prepared using polyols with 90, 110, 130, and 150 isocyanate index. The effect of sea water on the physical properties of PUF with the increase in isocyanate (NCO) index and ageing time was investigated. Tensile strengths and compressive strengths of the PUFs decreased up to 10% and 7% with an increase in ageing time, respectively. Cell morphology of the PUF under sea water was turned out to be the same as that in the ambient condition. It was observed that $T_g$ and tensile modulus of the PUF under sea water increased. The results showed an additional cross-link reaction of non-reacted MDI and the change of NCO peak as observed from FT-IR spectrum.

• Applied Chemistry for Engineering
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• v.16 no.3
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• pp.379-384
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• 2005

Polyurethane foams (PUFs) were prepared from polymeric 4,4'-diphenylmethane diisocyanate (PMDI), seven polyols with different functionalities and OH values, silicone surfactant, two catalysts, and three blowing agents. Chlorofluorocarbon (CFC-11), hydrochlorofluorocarbon (HCFC-141b) and hydrofluorocarbon (HFC-365mfc) were used as blowing agents. The effect of gelling and blowing catalysts on basic properties and cell structure of PUF with HCFC-141b was investigated. The cell size of the PUF decreased with an increase in the amount of catalyst from 0 to 2 pph (parts per hundred polyol). In the case of gelling type catalyst, the compressive strength increased from 11.9 to $12.66kg_f/cm^2$ with an increase in the amount catalyst from 0 to 2 pph but the density did not change significantly. The gelling time, density, and compressive strength of the PUF with three different blowing agents were measured. There was no detectable change in their properties. However, the cell structure of PUF with HCFC-141b was not uniform as in the other systems.

• Journal of Korean Neurosurgical Society
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• v.63 no.2
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• pp.137-152
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• 2020

In spite of the developing endovascular era, large (15-25 mm) and giant (>25 mm) wide-neck cerebral aneurysms remained technically challenging. Intracranial flow-diverting stents (FDS) were developed to address these challenges by targeting aneurysm hemodynamics to promote aneurysm occlusion. In 2011, the first FDS approved for use in the United States market. Shortly thereafter, the Pipeline of Uncoilable or Failed Aneurysms (PUFS) study was published demonstrating high efficacy and a similar complication profile to other intracranial stents. The initial FDA instructions for use (IFU) limited its use to patients 22 years old or older with wide-necked large or giant aneurysms of the internal carotid artery (ICA) from the petrous segment to superior hypophyseal artery/ophthalmic segment. Expanded IFU was tested in the Prospective Study on Embolization of Intracranial Aneurysms with PipelineTM Embolization Device (PREMIER) trial. With further post-approval clinical data, the United States FDA expanded the IFU to include patients with small or medium, wide-necked saccular or fusiform aneurysms from the petrous ICA to the ICA terminus. However, IFU is more restrictive in South Korea than in United States. Several systematic reviews and meta-analyses have sought to evaluate the overall efficacy of FDS for the treatment of cerebral aneurysms and consistently identify FDS as an effective technique for the treatment of aneurysms broadly with complication rates similar to other traditional techniques. A growing body of literature has demonstrated high efficacy of FDS for small aneurysms; distal artery aneurysms; non-saccular aneurysms posterior circulation aneurysms and complication rates similar to traditional techniques. In the short interval since the Pipeline Embolization Device was first introduced, FDS has been firmly entrenched as a powerful tool in the endovascular armamentarium. As new FDS are developed, established FDS are refined, and delivery systems are improved the uses for FDS will only expand further. Researchers continue to work to optimize the mechanical characteristics of the FDS themselves, aiming to optimize deploy ability and efficacy. With expanded use for small to medium aneurysms and posterior circulation aneurysms, FDS technology is firmly entrenched as a powerful tool to treat challenging aneurysms, both primarily and as an adjunct to coil embolization. With the aforementioned advances, the ease of FDS deployment will improve and complication rates will be further minimized. This will only further establish FDS deployment as a key strategy in the treatment of cerebral aneurysms.

• KIPS Transactions on Software and Data Engineering
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• v.6 no.9
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• pp.429-436
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• 2017

Unmanned Aerial Vehicles (UAV) that are piloted without human pilots can be commanded remotely via frequencies or perform pre-inputted missions. UAVs have been mainly used for military purposes, but due to the development of ICT technology, they are now widely used in the private sector. Teal Group's 2014 World UAV Forecast predicts that the UAV market will grow by 10% annually over the next decade, reaching $ 12.5 billion by 2023. However, because UAVs are primarily remotely controlled, if a malicious user accesses a remotely controlled UAV, it could seriously infringe privacy and cause financial loss or even loss of life. To solve this problem, a secure channel must be established through mutual authentication between the UAV and the control center. However, existing security techniques require a lot of computing resources and power, and because communication distances, infrastructure, and data flow are different from UAV networks, it is unsuitable for application in UAV environments. To resolve this problem, the study presents a lightweight UAV authentication method based on Physical Unclonable Functions (PUFs) that requires less computing resources in the ground Control and Non-Payload Communication (CNPC) environment, where recently, technology standardization is actively under progress.

• Koreanishche Zeitschrift fur Deutsche Sprachwissenschaft
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• v.4
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• pp.395-411
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• 2001

Die $W\"{o}rterb\"{u}cher$ spielen beim Erwerb einer Sprache eine wesentliche Rolle. Es gibt inzwischen mehrere Deutsch-Koreanische $W\"{o}rterb\"{u}cher$. Die Lage $f\"{u}r$ die Koreanisch-Deutschen $W\"{o}rterb\"{u}cher$ ist aber verbesserungs- $bed\"{u}rftig$. Stellvertretend $f\"{u}r$ das Koreanisch/Deutsche $W\"{o}rterbuch$ steht das 1981 von der Koreanischen Gesellschaft $f\"{u}r$ Germanistik nach $zehnj\"{a}hriger$ Arbeit fertiggestellte Essence Koreanisch-Deutsche $W\"{o}rterb\"{u}ch$ (Minjung seorim 1982). Dieses $W\"{o}rterb\"{u}ch$ weist aber einige Nachteilen auf. Es fehlen jegliche Angaben zum Korpus. Man $st\"{o}{\ss}t$ beispielsweise oft auf selten gebrauchte $W\"{o}rter$, die Grundbedeutungen sind nicht erkennbar, die Erklarungen sind ungenau, manchmal sogar $irref\"{u}hrend\;und\;schlie{\ss}lich$ mitunter stilistisch falsch. Diese negativen Punkte wirken sich $ung\"{u}nstig$ auf den gesamten Lemprozess bis hin zur Lemmotivation aus. Aus diesen Gegebenheiten $erw\"{a}chst$ die Notwendigkeit der Erstellung eines neuen $W\"{o}rterb\"{u}ch$s, das auf die Situation von Sprachlemem abgestimmt ist, die zur Benutzung einsprachiger $W\"{o}rterbticher$ noch nicht imstande sind. Zweck des $W\"{o}rterb\"{u}chs$ ist der Einsatz im Fremdsprachenunterricht, woraus sich ein zweisprachiges $W\"{o}rterb\"{u}ch$ ergibt. Als Benutzerkreis werden insbesondere $Sprachlemanf\"{a}nger$ des Koreanischen und Deutschen ins Auge gefasst. Ihnen soll ein Nachschlagewerk an die Hand gegeben werden, das den koreanischen und deutschen Wortschatz anhand einer Systematik und eines alphabetischen Indexes der jeweiligen Sprache $erschlie{\ss}t$. Ais Zahl der Lemmata wird $f\"{u}r$ jede Sprache ca. 10,000 festgelegt. Ein Grundwortschatz, der die 3000 $h\"{a}ufigsten\;W\"{o}rter$ umfasst wird extra markiert. $Dar\"{u}ber$ hinaus bietet das $W\"{o}rterb\"{u}ch$ den darauf aufbauende Wortschatz von weiteren 7000 $W\"{o}rtern$. Die Teamarbeit der beiden Gruppen von Muttersprachlern steht in allen Arbeitsschritten im Vordergrund. Der damit verbundene Zweck ist die Erzielung der maximalen Genauigkeit der $Lemmaerkl\"{a}rungen$. Da dieses $W\"{o}rterb\"{u}ch$ ein $W\"{o}rterb\"{u}ch$ nach Sachgruppen ist, die Erstellung einer Systematik von $gro{\ss}er$ Bedeutung. $F\"{u}r$ das vorliegende Projekt gait daher eine Systematik zu finden, die nicht nur leicht nachvollziehbar, also praktikabel ist, sondern insbesondere von Benutzern aus zwei Kulturkreisen akzeptiert werden kann. Als $grunds\"{a}tzliche$, allerdings nicht in allen Bereichen $gleicherma{\ss}en$ anwendbare Ordnungsprinzipien gelten: Vom Oberbegriff zum Unterbegriff, vom allgemein zum speziell, vom Einfach zum Komplexen, von $au{\ss}en$ nach innen, Darin spiegelt sich das Prinzip der 'notwendigen Bedingung' wider.

• Polymer(Korea)
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• v.29 no.5
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• pp.457-462
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• 2005

Polyurethane foams (PUFs) were prepared from polymeric 4,4'-diphenylmethane diisocyanate (PMDI), mixed polyol with OH value of 480, silicone surfactant, three catalysts, and hydrofluorocarbon(HFC) as blowing agent. Balance (PC-8), gelling (33LV), and trimerization (TMR-2) catalysts were used. The effect of the catalysts on the physical properties of PUF with increase of isocyanate (NCO) index and aging time was investigated. The cell size of the PUF with PC-8 and 33LV slightly increased with an increase in NCO index from 100 to 170 but compressive strength did not change significantly. In case of trimerization catalyst, the compressive strength of PUF increased from 8.75 to 1$10.5 kg_f/cm^2$ and the cell size decreased with an increase in NCO index. The compressive strength of the PUF with 33LV increased from 9.21 to $10.15 kg_f/cm^2$ with an increase in aging time. However, there was no detectable change in the compressive strength of PUF with TMR-2. A possible interpretation of the results includes an additional cross-link reaction of non-reacted MDI and FTIR spectrum illustrated the change of NCO peak.