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Analysis of Air Flow inside the Compartment under Backdraft Conditions using Solid Combustibles
Jaeseong An(Jaeseong An),Taehoon Kim(Taehoon Kim) 한국화재소방학회 2022 International Journal of Fire Science and Engineer Vol.36 No.2
Backdraft is a phenomenon of explosive combustion that occurs when fire in a state of smoldering due to the lack of oxygen grows as the air is admitted after opening the entrance door or window. In this study, a reduced compartment was produced to simulate a backdraft. In an actual site, the fire was generated by solid combustibles, and hence, wood pieces were used to generate the backdraft in this study. Twenty-seven thermocouples were installed inside the compartment. One side of a wall consists of polycarbonate and the interior of the compartment was monitored using a camera. An additional fire simulation was performed using a fire dynamics simulator for in-depth analysis of the phenomena inside the compartment. In the experiment, the air flown into the compartment through the vent opening turned the smoldering fire of solid combustibles into the flaming fire, which led to the ignition of flammable gas inside the compartment. Next, the propagation of the flame was first directed upwards to the combustibles, then towards the center, and ultimately to the exterior. This phenomenon was observed in the analysis of the compartment holding a homogeneous flammable mixture. The results of the analysis showed that the flammable mixture on the interior was released to the exterior because of the rise in the internal pressure caused by flame propagation. Consequently, as the internal flame was propagated to the exterior, the mixture was ignited. Thus, the phenomenon of backdraft in the case of compartment fire was shown to occur as follows. First, the air flown in via the vent opening was elevated to the upper part of the compartment by the smoldering heat on the interior. Next, the flame led to the ignition of the flammable mixture formed on the upper part.
Template-engineered epitaxial BiVO<sub>4</sub> photoanodes for efficient solar water splitting
Song, Jaesun,Cha, Jaeseong,Lee, Mi Gyoung,Jeong, Hye Won,Seo, Sehun,Yoo, Ji Ae,Kim, Taemin Ludvic,Lee, Jongmin,No, Heesung,Kim, Do Hyun,Jeong, Sang Yun,An, Hyunji,Lee, Byoung Hun,Bark, Chung Wung,Park Royal Society of Chemistry 2017 Journal of Materials Chemistry A Vol.5 No.35
<▼1><P>The photoelectrochemical properties of template-engineered epitaxial BiVO4 photoanodes have been enhanced approximately 10 times that of bare BiVO4.</P></▼1><▼2><P>Bismuth vanadate (BiVO4) has attracted significant attention as a promising photoanode material for hydrogen production <I>via</I> photoelectrochemical (PEC) water splitting because of its narrow optical band gap and suitable band edge positions for water oxidation. However, the actual photoactivity of BiVO4 is considerably limited by its poor electron transport and slow water oxidation kinetics. Although several studies have been carried out to improve its photo-efficiency <I>via</I> the enhancement of electron transport and water oxidation kinetics, only a few studies have reported the growth of epitaxial BiVO4 to explore the fundamental properties of BiVO4 for PEC water splitting because extremely flat epitaxial films exhibit poor photo-efficiency because of their low surface-active area. However, studies of epitaxial BiVO4 still have the potential to provide new routes for improving its photo-efficiency. In this study, the growth of epitaxial BiVO4 is investigated using a thin γ-WO3 template layer deposited on a SrTiO3(001) substrate covered by a SrRuO3 (SRO) bottom electrode using pulsed laser deposition. Consequently, at 1.23 V <I>vs.</I> the RHE (reversible hydrogen electrode), the photocurrent density of epitaxial BiVO4 on the γ-WO3 template layer (2.20 mA cm<SUP>−2</SUP>) is approximately 10 times that of bare BiVO4, related to the effective charge transfer by the γ-WO3 intermediate layers and the subsequent increase in the surface-active area of epitaxial BiVO4. These results strongly suggest that epitaxial BiVO4 grown using a template layer can be a cornerstone for the in-depth understanding of the fundamental properties of BiVO4 for PEC water splitting.</P></▼2>
Song, Jaesun,Kim, Taemin Ludvic,Lee, Jongmin,Cho, Sam Yeon,Cha, Jaeseong,Jeong, Sang Yun,An, Hyunji,Kim, Wan Sik,Jung, Yen-Sook,Park, Jiyoon,Jung, Gun Young,Kim, Dong-Yu,Jo, Ji Young,Bu, Sang Don,Jang Springer-Verlag 2018 NANO RESEARCH Vol.11 No.2
<P>In photoelectrochemical (PEC) water splitting, charge separation and collection by the electric field in the photoactive material are the most important factors for improved conversion efficiency. Hence, ferroelectric oxides, in which electrons are the majority carriers, are considered promising photoanode materials because their high built-in potential, provided by their spontaneous polarization, can significantly enhance the separation and drift of photogenerated carriers. In this regard, the PEC properties of BiFeO3 thin-film photoanodes with different crystallographic orientations and consequent ferroelectric domain structures are investigated. As the crystallographic orientation changes from (001)(pc) via (110)(pc) to (111)(pc), the ferroelastic domains in epitaxial BiFeO3 thin films become mono-variant and the spontaneous polarization levels increase to 110 mu C/cm(2). Consequently, the photocurrent density at 0 V vs. Ag/AgCl increases approximately 5.3-fold and the onset potential decreases by 0.180 V in the downward polarization state. It is further demonstrated that ferroelectric switching in the (111)(pc) BiFeO3 thin-film photoanode leads to an approximate change of 8,000% in the photocurrent density and a 0.330 V shift in the onset potential. This study strongly suggests that domain-engineered ferroelectric materials can be used as effective charge separation and collection layers for efficient solar water-splitting photoanodes.</P>
An Jae Seong,Kim Do Hyun 대한비과학회 2023 Journal of rhinology Vol.30 No.2
An inverted papilloma of the frontal sinus is a challenging lesion for surgeons, for both anatomical and pathological reasons. Despite the trend away from an external approach and towards an endonasal endoscopic approach, indications for an external approach remain. The options for an external approach include endoscopic frontal trephination, transpalpebral orbital craniotomy, a supraorbital transeyebrow approach, an osteoplastic flap, and bifrontal craniotomy with cranialization. Each approach has advantages and disadvantages. Deciding on the appropriate approach is important for the patient’s prognosis and risk of complications. We report two cases of frontal sinus inverted papilloma treated with a combined bifrontal craniotomy with cranialization and endonasal endoscopic approach. We also present a general review of the external approaches mentioned above.
An Jae Seong,Kim Do Hyun,Kim Soo Whan,Kim Sung Won,Lee Il Hwan 대한비과학회 2023 Journal of rhinology Vol.30 No.1
Background and Objectives: We compared pain levels, cardiovascular parameters, and complications according to whether patients underwent nasal packing with non-absorbable or biodegradable materials. Methods: Patients who underwent septoplasty from May 2015 to April 2020 were retrospectively reviewed. Numeric rating scale (NRS) scores for pain, blood pressure, and heart rate were measured three times (immediately after surgery, 6 hours later, and on postoperative day [POD] 1). We collected data on complications, including postoperative bleeding, septal hematoma, adhesions, septal perforation, and the recurrence of septal deviation. Results: In total, 200 patients underwent septoplasty, of whom 100 underwent nasal packing with Merocel and 100 underwent packing with Nasopore. The summed NRS scores over the three time points did not differ significantly between the groups. The NRS scores at 6 hours after surgery were highest in both groups. The systolic and diastolic blood pressure and the heart rate immediately after surgery were significantly higher than before surgery in both groups. The blood pressure and heart rate at 6 hours after surgery and on POD 1 did not differ significantly from those before surgery in either group. The incidence of sleep disturbance, postoperative bleeding, septal hematoma, adhesions, septal perforation, and recurrence of septal deviation did not differ significantly between the two groups. Conclusion: Although the level of postoperative pain and the cardiovascular parameters changed over time, we found no significant differences in pain, blood pressure, heart rate, or the complication rate according to whether patients underwent nasal packing with Nasopore or Merocel.