• Korean Chemical Engineering Research
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• v.49 no.4
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• pp.460-464
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• 2011

Poly(ether-block-amide)(PEBA, $PEBAX^{TM}$) resin is a thermoplastic elastomer combining linear chains of hard-rigid polyamide block interspaced soft-flexible polyether block. It was believed that the hard polyamide block provides the mechanical strength and permeation selectivity, whereas gas transport occurs primarily through the soft polyether block. The objective of this work was to investigate the gas permeation properties of carbon dioxide and methane for $PEBAX^{TM}$-1657 membrane and compare with those obtained for other grade of $PEBAX^{TM}$, $PEBAX^{TM}$-2533. And the organic/inorganic hybrid membranes were prepared using $PEBAX^{TM}$ and TEOS(tetraethoxysilane) by sol-gel process, and gas permeation properties were studied. $PEBAX^{TM}$-2533 membrane exhibited higher gas permeability coefficients than $PEBAX^{TM}$-1657 membrane. This was explained by the increase of chain mobility. The permeability coefficients for $PEBAX^{TM}$/TEOS hybrid membranes were higher than pure $PEBAX^{TM}$ membranes. This results were explained by the reduction of crystallinity of polyamide block by the introduction of TEOS. Ideal separation factor of hybrid membranes does not change much. This might be due to the increase of solubility selectivity.

• Journal of the Korean Geotechnical Society
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• v.21 no.3
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• pp.5-17
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• 2005

Spatial uncertainty of Busan marine clay ground, which commonly occurs during site investigation testing, data analysis and transformation modeling, has been described. In this paper geotechnical uncertainty of shear strength indicator $N_k$ has been quantified in both horizontal direction and vertical direction using geostatistical Kriging method. Most of soil data used are from 25 boring tests, 75 laboratory tests, 124 field vane tests and 25 cone penetration tests (CPT). CPT-$N_k$ data for undrained shear strength determination, which are the most important properties in geotechnical design stages, have been analysed. Comparison between cone factor from conventional CPT-based method and that of geostatistical method shows that geostatistical Kriging method is an ideal tool to quantify the spatial variability of uncertainty from self-correlation of soil property of interest, and can be recommended to identify the spatial distribution of consolidation .md shear strength of soils at any sites concerned.

• Archives of Plastic Surgery
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• v.36 no.4
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• pp.489-492
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• 2009

Purpose: Autologous fat injection is ideal for patients who wish to add contour, projection and gross volumization of the aging, atrophic face and is claimed to be a safe procedure. However, there are several case reports in the literature where patients have suffered from acute visual loss and cerebral infarction after facial fat injection. This paper will explore a rare case of vessel related complication, an arteriovenous fistula that occurs after fat injection on forehead. Method: A 28 - year - old female who showed a non - tender, soft $1.0{\times}2.5cm$ sized mass on forehead for 3 weeks. A thrill could be detected on the totuous dilatated vessel - like structure around the mass. She had a fat injection on forehead for soft tissue augmentation 3 months prior to developing the mass. 3 - dimensional brain CT angiography showed arteriovenous fistula. Results: The fistula is totally excised with ligation of feeding vessels. Pathology report showed an atypical vessel which had intimal thickening, myxoid degeneration and thrombus formation. There were no evidences of recurrence at least for 2 months of follow - up. Conclusion: An occurrence of arteriovenous fistula after autologous fat injection is very rare. After perforation of artery and vein by coincidence, blood extravasates with the formation of a hematoma capsule and a pseudocapsule around it. The hematoma capsule would expand and clot would reabsorb resulting in a cavity leading to fistula formation. Other vessel related complications like acute visual loss or cerebral infarction are very severe. Therefore, surgeons should be cautious during facial fat injection to avoid vessel injuries.

• Archives of Plastic Surgery
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• v.40 no.3
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• pp.226-231
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• 2013

Background The reconstruction of volar surface defects is difficult because of the special histologic nature of the tissue involved. The plantar surface is the most homologous in shape and function and could be considered the most ideal of reconstructive options in select cases of volar surface defects. In this paper, we evaluate a single institutional case series of volar tissue defects managed with second toe plantar free flaps. Methods A single-institution retrospective review was performed on 12 cases of reconstruction using a second toe plantar free flap. The mean age was 33 years (range, 9 to 54 years) with a male-to-female ratio of 5-to-1. The predominant mechanism was crush injury (8 cases) followed by amputations (3 cases) and a single case of burn injury. Half of the indications (6 cases) were for soft-tissue defects with the other half for scar contracture. Results All of the flaps survived through the follow-up period. Sensory recovery was related to the time interval between injury and reconstruction-with delayed operations portending worse outcomes. There were no postoperative complications in this series. Conclusions Flexion contracture is the key functional deficit of volar tissue defects. The second toe plantar free flap is the singular flap whose histology most closely matches those of the original volar tissue. In our experience, this flap is the superior reconstructive option within the specific indications dictated by the defect size and location.

• Journal of Dental Rehabilitation and Applied Science
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• v.29 no.4
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• pp.407-417
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• 2013

The one of peri-implant soft tissue problems seen during the maintenance phase of implant therapy is an inadequate zone of keratinized tissue. Keratinized tissue plays a major role around teeth and dental implants, helping in maintaining and facilitating oral hygiene. A free gingival graft (FGG) is chosen to correct the soft tissue defects and provide optimal peri-implant health in order to increase the long-term prognosis of the implant reconstruction. However, the patient treated with FGG has pain and discomfort on donor site such as palate. It is also technically demanding, time consuming, and the color match of the tissue is often less than ideal. An apically positioned flap (APF) is selected for increasing the keratinized tissue simply while or after the second stage implant surgery. This case report shows successfully increasing the width of peri-implant kenratinized tissue through APF procedure on small site of dental implant instead of FGG.

• Journal of the Korean Magnetics Society
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• v.5 no.5
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• pp.366-371
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• 1995

High performance magnetic materials are characterized by the combination of outstanding magnetic properties and optimized microstructures, e.g., nanocrystalline composites of multilayers and small particle systems. The characteristic parameters of the hysteresis loops of these materials vary over more than a factor of $10^{6}$ with optimum values for the coercive field of several Tesla and permeabilities of $10^{6}$. Within the framework of the computational micromagnetism (nanomagnetism) using the finite element method the upper and lower bounds of the coercive field of different types of grain ensembles and multilayers have been determined. For the case of nanocrystalline composites the role of grain size, exchange and dipolar coupling between grains and the degree of grain alignment will be discusses in detail. It is shown that the largest coercivities are obtained for exchange decoupled grains, whereas remanence enhancing requires exchange coupled grains below 20 nm. For composite permanent magnets based on $Nd_{2}Fe_{14}B$ with an amount of ~ 50% soft $\alpha$-Fe-phase coercivities of ${\mu}_{0}H_{c}=0.75\;T$, a remanence of 1.5 T and an energy product of $400\;kJ/m^{3}$ is expected. In nanocrystalline systems the temperature dependence of the coercivity is well described by the relation ${\mu}_{0}H_{c}=(2\;K_{1}/M_{s}){\alpha}-N_{eff}{\mu}_{0}M_{s}$, where the microstructural parameters $\alpha$ and $N_{eff}$ take care of the short-range perturbations of the anisotropy and $N_{eff}$ is related to the long-range dipolar interactions. $N_{eff}$ is found to follow a logarithmic grain size size dependence ${\mu}_{0}H_{c}=(2\;K_{1}/M_{s}){\alpha}-N_{eff}(\beta1nD){\mu}_{0}M_{s}$. Several trends how to achieve the ideal situation $\alpha$->1 and $N_{eff}$->1->0 will be discussed.

• Korean Chemical Engineering Research
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• v.54 no.5
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• pp.653-658
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• 2016

Poly(ether-block-amide)(PEBAX$_{(R)}$) resin is a thermoplastic elastomer combining linear chains of hard-rigid polyamide block interspaced soft-flexible polyether block. It was believed that the hard polyamide block provides the mechanical strength and permselectivity, whereas gas transport occurs primarily through the soft polyether block. The objective of this work was to investigate the gas permeation properties of carbon dioxide and methane for PEBAX$^{(R)}$-1657 membrane, and compare with those obtained for other grade of pure PEBAX$^{(R)}$, PEBAX$^{(R)}$-2533 and PEBAX$^{(R)}$ based hybrid membranes. The hybrid membranes based PEBAX$^{(R)}$ were obtained by a sol-gel process using GPTMS ((3-glycidoxypropyl) trimethoxysilane) as the only inorganic precursor. Molecular structure and morphology of membrane were analyzed by $^{29}Si$-NMR, DSC and SEM. PEBAX$_{(R)}$-2533 membrane exhibited higher gas permeability coefficients than PEBAX$^{(R)}$-1657 membrane. This was explained by the increase of chain mobility. In contrast, ideal separation factor of $CO_2/CH_4$ for PEBAX$^{(R)}$-1657 membrane was higher than PEBAX$^{(R)}$-2533 membrane. It was explained by the decrease of diffusion selectivity caused by increase of chain mobility. For PEBAX$^{(R)}$/GPTMS hybrid membrane, gas permeability coefficients were decreased with reaction time. Gas permeability coefficient of $CH_4$ was more significantly decreased than $CO_2$. It can be explained by the reduction of chain mobility caused by the sol-gel process, and strong affinity of PEO segment with $CO_2$. Comparing with pure PEBAX$^{(R)}$-1657 membrane, ideal separation factor of $CO_2/CH_4$ for PEBAX$^{(R)}$/GPTMS hybrid membrane has decreased to 4.5%, and gas permeability coefficient of $CO_2$ has increased 3.5 times.

• Korean Journal of Cleft Lip And Palate
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• v.15 no.1
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• pp.39-50
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• 2012

A submucous cleft palate(SMCP) is characterized by a midline deficiency or lack with/without incorrect positioning of muscular tissues in the soft palate, and by a bony defect in the midline or the center of the hard palate. Velopharyngeal incompetence(VPI) related to this SMCP has been managed by various surgical and prosthetic techniques. Because the individual diagnosis and treatment of SMCP patients was not easy to the speech pathologist and to the maxillofacial reconstructive surgeons, and for the better understanding and for the ideal approaches to the SMCP patients, we reviewed several recent articles about grading system in the SMCP caused by VPI, and summarized in this review article.

• Proceedings of the IEEK Conference
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• 2004.06a
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• pp.43-46
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• 2004

In this paper, we present a carrier phase estimation algorithm for LDPC coded systems. LDPC coded system can not achieve the ideal performance if phase offset is introduced by channel. However, the estimation of phase offset is very hard since the operating point of LDPC is very low SNR. To solve this problem, the algorithm using the tentative soft decision value and based on Maximum Likelihood (ML), was proposed in [2]. But this algorithm has problem which works only under constant phase offset. If phase offset is time variant, it has a severe degradation in performance. To solve this problem. we propose two types of estimators. symbol by symbol estimator: Unidirectional estimator (UDE) and hi-directional estimator (BDE), and sub-block estimator (SBE).

• Archives of Reconstructive Microsurgery
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• v.9 no.2
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• pp.110-113
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• 2000

The reconstruction of soft tissue defects of the sole requires to stand the force of weight bearing, provide sensation and adequacy for normal foot-wear. Although certain local flaps have been described and used for resurfacing the foot, extensive injury requires distant or free flaps for coverage. There is no doubt that the ideal tissue for resurfacing the sole is the plantar tissue itself. The specialized dermal-epidermal histology and fibrous septa of the subcutaneous layer gives its unique property to stand the pressure and to absorb the shock upon gait. This paper presents a case of reconstructing the sole that involves about 70% of the weight bearing portion. The combined medial plantar and dorsalis pedis chimeric free flap based on the medial plantar artery and medial plantar nerve adds another dimension in resurfacing the weight bearing sole of moderate to large sized defects.