• Journal of Korean Neurosurgical Society
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• v.65 no.6
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• pp.779-789
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• 2022

Objective : To analyze the effects of the number and shape of fenestrations on the mechanical strength of pedicle screws and the effects of bone cement augmentation (BCA) on the pull-out strength (POS) of screws used in conventional BCA. Methods : For the control group, a conventional screw was defined as C1, a screw with cannulated end-holes was defined as C2, a C2 screw with six pinholes was defined as C3, and the control group type was set. Among the experimental screws, T1 was designed using symmetrically placed thru-hole type fenestrations with an elliptical shape, while T2 was designed with half-moon (HM)-shaped asymmetrical fenestrations. T3 and T4 were designed with single HM-shaped fenestrations covering three pitches and five pitches, respectively. T5 and T6 were designed with 0.6-mm and 1-mm wider fenestrations than T3. BCA was performed by injecting 3 mL of commercial bone cement in the screw, and mechanical strength and POS tests were performed according to ASTM F1717 and ASTM F543 standards. Synthetic bone (model #1522-505) made of polyurethane foam was used as a model of osteoporotic bone, and radiographic examinations were performed using computed tomography and fluoroscopy. Results : In the fatigue test, at 75% ultimate load, fractures occurred 7781 and 9189 times; at 50%, they occurred 36122 and 82067 times; and at 25%, no fractures occurred. The mean ultimate load for each screw type was 219.1±52.39 N for T1, 234.74±15.9 N for T2, 220.70±59.23 N for T3, 216.45±32.4 N for T4, 181.55±54.78 N for T5, and 216.47±29.25 N for T6. In comparison with C1, T1, T2, T3, T4, and T6 showed significantly different ultimate load values (p<0.05). However, when the values for C2 and the fenestrated screws were evaluated with an unpaired t test, the ultimate load value of C2 significantly differed only from that of T2 (p=0.025). The ultimate load value of C3 differed significantly from those of T1 and T2 (C3 vs. T1 : p=0.048; C3 vs. T2 : p<0.001). Linear correlation analysis revealed a significant correlation between the fenestration area and the volume of bone cement (Pearson's correlation coefficient r=0.288, p=0.036). The bone cement volume and ultimate load significantly correlated with each other in linear correlation analysis (r=0.403, p=0.003). Conclusion : Fenestration yielded a superior ultimate load in comparison with standard BCA using a conventional screw. In T2 screws with asymmetrical two-way fenestrations showed the maximal increase in ultimate load. The fenestrated screws can be expected to show a stable position for the formation of the cement mass.

• Journal of Mushroom
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• v.21 no.4
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• pp.241-246
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• 2023

Flammulina velutipesis a popular edible mushroom in South Korea, accounting for approximately 30% of the total mushroom export in the country. Despite its significant position in the domestic mushroom industry, approximately 65% of the cultivated F. velutipes are foreign varieties. To secure variety rights and enhance competitiveness in the export market, there is a need to develop domestic varieties with stable production and excellent shelf life. We focused on breeding a new variety called 'Baekwoon' through mon-mon crossing, using 'Baekseung' and an international collection strain (KMCC02260) as parents. Baekwoon exhibited faster mycelial growth rates at 15 ℃ and 25 ℃ and higher mycelial growth across four tested media compared to that of the control variety. Under bottle cultivation, Baekwoon had a mycelial cultivation period that was shorter by approximately 2 days compared to that of the control. The yield of Baekwoon was 228.0±10.9 g, 8.3% more than that of the control. Furthermore, Baekwoon displayed distinct morphological features characterized by a larger pileus and thicker stipe compared to that of the control variety. Genetic tests confirmed that Baekwoon is genetically different from both parental strains and the control variety. It is expected that the newly developed F. velutipes variety, Baekwoon, will be evaluated for its adaptation in different regions and actively promoted in the field, ultimately increasing the market share of domestic varieties.

• Bulletin of the Korean Chemical Society
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• v.23 no.1
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• pp.132-136
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• 2002

$Pt(2,6-(Cy_2PCH_2)_2C_6H_3)(OTf)\;(OTf=CF_3SO_3^-)$ readily reacts with various amines to afford cationic amine complexes $[Pt(2,6-(Cy_2PCH_2)_2C_6H_3)(amine)](OTf)\;(amine=NH_3,\;NHMe_2,\;NHC_4H_8,\;NH_2Ph,\;NH_2(Tol-p))$ in high yields. These complexes have been fully characterized by IR, $^1H-,\;^{19}F{^1H}-,\;and\;^{31}P{^1H}-NMR$ spectroscopy, and elemental analyses. Reaction of $Pt(2,6-(Cy_2PCH_2)_2C_6H_3)(OTf)$ with acrylonitrile quantitatively produced the ${\pi}$-olefinic complex $Pt(2,6-(Cy_2PCH_2)_2C_6H_3)(CH_2=CHCN)](OTf)$ which is only stable in solution in the presence of acrylonitrile. Attempt at isolating this complex in the pure solid state was failed due to partial decomposition into $Pt(2,6-(Cy_2PCH_2)_2C_6H_3)(OTf)$ The equilibrium constants $(K_{eq}=[Pt(PCP)-(NH_2R)^+][CH_2=CHCN]/[Pt(PCP)(CH_2=CHCN)^+][NH_2R]:\;[Pt(2,6-(Cy_2PCH_2)_2C_6H_3)(CH_2=CHCN)]^++NH_2R{\rightleftarrows}[Pt(2,6-(Cy_2PCH_2)_2C_6H_3)(NH_2R)]^++CH_2=CHCN=Ph,\;p-tolyl)$ were calculated to be 0.28 (for R = Ph) and 3.1 (R = p-tolyl) at $21^{\circ}C$. The relative stability of the ${\sigma}$-donor amine versus the ${\pi}$-olefinic acrylonitrile complex has been found largely dependent upon the amine-basicity $(pK_b)$, implicating that acrylonitrile practically competes with amine in the platinum coordination sphere. On the contrary to the formation of the acrylonitrile complex, no reaction of $Pt(2,6-(Cy_2PCH_2)_2C_6H_3)(OTf)$ with other olefins such as ethylene, styrene and methyl acrylate was observed.

• Bulletin of the Korean Chemical Society
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• v.27 no.9
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• pp.1297-1304
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• 2006

A systematic study of the structure, energetics and spectral characteristics of substituted aminoketenes $R(NH_2)$C=C=O (R = H, $CH_3$, $NH_2$, OH, $OCH_3$, CH=$CH_2$, C$\equiv$CH, CN, CHO, NO, $NO_2$) which are highly reactive and transient intermediates in synthesis has been conducted by ab initio calculations at the MP2/6- 31G*//MP2/6-31G* level. Twenty four stable isomers of the eleven substituted aminoketenes having dihedral angles $\phi NH_2\sim120{^{\circ}}$ and $60^{\circ}$ have been identified and their optimized geometries and energies obtained. Electrostatic and steric effects on the molecular geometries have been analyzed. While the $\pi$-acceptor groups lead to planar conformations, the electron-donor groups give rise to non-planar conformations. Isodesmic substituent stabilization energies relative to alkenes have been calculated and correlation with group electronegativities established. Role of induction effect by the substituent groups and resonance effects in charge distribution in the molecules has been analyzed. An analysis of the asymmetric stretching frequencies and intensities of the C=C=O group shows that affect of non-$\pi$ acceptor substituents on the frequency is determined by the field effect (F) and resonance effect (R) parameters, the calculated intensities I (km/mol.) are correlated to group electronegativities $x$ of the substituents by the relationship I = 640.2–100.1 $x$ (r = 0.92). The $\pi$-acceptor substituents increase the intensity which may be explained in terms of their delocalizing effect on the negative charge at the $C_{\beta}$ atom.

• Applied Microscopy
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• v.47 no.3
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• pp.110-120
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• 2017

Non-isothermal thermogravimetry (TG) measurements on melt-quenched $Bi_xSe_{100-x}$ specimens (x=0, 2.5, 7.5 at%) were made at a heating rate ${\beta}=10^{\circ}C/min$ in the range $T=35^{\circ}C{\sim}950^{\circ}C$. The as-measured TG curves confirm that $Bi_xSe_{100-x}$ samples were thermally stable with minor loss at $T{\leq}400^{\circ}C$ and mass loss starts to decrease up to $600^{\circ}C$, beyond which trivial mass loss was observed. These TG curves were used to estimate molar (Se/Bi)-ratios of $Bi_xSe_{100-x}$ samples, which were not in accordance with initial composition. Shaping features of conversion curves ${\alpha}(T)-T$ of $Bi_xSe_{100-x}$ samples combined with a reliable flow chart were used to reduce kinetic mechanisms that would have caused their thermal mass loss to few nth-order reaction models of the form $f[{\alpha}(T)]{\propto}[1-{\alpha}(T)]^n$ (n=1/2, 2/3, and 1). The constructed ${\alpha}(T)-T$ and $(d{\alpha}(T)/dT)-T$ curves were analyzed using Coats-Redfern (CR) and Achar-Brindley-Sharp (ABS) kinetic formulas on basis of these model functions, but the linearity of attained plots were good in a limited ${\alpha}(T)-region$. The applicability of CR and ABS methods, with model function of kinetic reaction mechanism R0 (n=0), was notable as they gave best linear fits over much broader ${\alpha}(T)-range$.

• Korean Journal of Plant Taxonomy
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• v.46 no.2
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• pp.129-148
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• 2016

Plant species on oceanic islands comprise nearly 25% of described vascular plants on only 5% of the Earth's land surface yet are among the most rare and endangered plants. Conservation of plant biodiversity on islands poses particular challenges because many species occur in a few and/or small populations, and their habitats on islands are often disturbed by the activity of humans or by natural processes such as landslides and volcanoes. In addition to described species, evidence is accumulating that there are likely significant numbers of "cryptic" species in oceanic archipelagos. Plant systematists, in collaboration with others in the botanical disciplines, are critical to the discovery of the subtle diversity in oceanic island floras. Molecular data will play an ever increasing role in revealing variation in island lineages. However, the input from plant systematists and other organismal biologists will continue to be important in calling attention to morphological and ecological variation in natural populations and in the discovery of "new" populations that can inform sampling for molecular analyses. Conversely, organismal biologists can provide basic information necessary for understanding the biology of the molecular variants, including diagnostic morphological characters, reproductive biology, habitat, etc. Such basic information is important when describing new species and arguing for their protection. Hybridization presents one of the most challenging problems in the conservation of insular plant diversity, with the process having the potential to decrease diversity in several ways including the merging of species into hybrid swarms or conversely hybridization may generate stable novel recombinants that merit recognition as new species. These processes are often operative in recent radiations in which intrinsic barriers to gene flow have not evolved. The knowledge and continued monitoring of plant populations in the dynamic landscapes on oceanic islands are critical to the preservation of their plant diversity.

• Bulletin of the Korean Chemical Society
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• v.27 no.5
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• pp.718-724
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• 2006

The heterogeneous association behaviour of various concentration binary mixtures of mono alkyl ethers of ethylene glycol with ethyl alcohol were investigated by dielectric measurement in benzene solutions over the entire concentration range at 25 ${^{\circ}C}$. The values of static dielectric constant $\epsilon_0$ of the mixtures were measured at 1 MHz using a four terminal dielectric liquid test fixture and precision LCR meter. The high frequency limiting dielectric constant $\epsilon_\infty$ values were determined by measurement of refractive index $n_D$ ($\epsilon_\infty\;=\;n_D\;^2$). The measured values of $\epsilon_0$ and $\epsilon_\infty$ were used to evaluate the values of excess dielectric constant $\epsilon^E$, effective Kirkwood correlation factor $g^{eff}$ and corrective correlation factor $g_f$ of the binary polar mixtures to obtain qualitative and quantitative information about the H-bond complex formation. The non-linear behaviour of the observed $\epsilon_0$ values of the polar molecules and their mixtures in benzene solvent confirms the variation in the associated structures with change in polar mixture constituents concentration and also by dilution in non-polar solvents. Appearance of the maximum in $\epsilon^E$ values at different concentration of the polar mixtures suggest the formation of stable adduct complex, which depends on the molecular size of the mono alkyl ethers of ethylene glycol. Further, the observed $\epsilon^E$ < 0 also confirms the heterogeneous H-bond complex formation reduces the effective number of dipoles in these polar binary mixtures. In benzene solutions these polar molecules shows the maximum reduce in effective number of dipoles at 50 percent dilutions. But ethyl alcohol rich binary polar mixtures in benzene solvent show the maximum reduce in effective number of dipoles in benzene rich solutions.

• The Transactions of the Korean Institute of Power Electronics
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• v.4 no.5
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• pp.433-441
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• 1999

This paper presents a S-FES(Superconducting magnetic becuing Flywheel Energy Storage System) for the p purpose of replacing battery used to store the energy. Especially, the design elements of FES, such as the b beming, wheel mateηaI, and power converter, etc., are described. The design and manufacturing techniques of t the controllable IXlwer converter are proposed to generate the sinusoidal output current in the high speed operation and to get the const빠synchronous motor with halbach cuTay of high coesive I\d-Fe-B permanent magnet is used as the driver of F FES. The proposed S-FES system shows the stable rotation characteristics at high speed range about l 10,000[rpm]. To verify the validity of proposed system, the comparative study with the conventional ball b beming s~rstem is proceeded and it is well confirmed with the result of the lower friction losses of S-FES S system.

• The Journal of Korean Academy of Prosthodontics
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• v.42 no.2
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• pp.133-141
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• 2004

Statement of problem : Porcelain restorations are widely used in restorative dentistry with a high degree of general success. However, porcelain is brittle and may fracture intraorally. Sometimes a repair may be attempted using composite resin and bonding system available. Color stability of porcelain repair resins affects esthetics and prognosis of prosthesis, so that provides important criteria for the choice of porcelain repair resins. Purpose : The purpose of this study was to investigate the color stability of composite resins used widely as porcelain repair system. Materials and method : Composite resins used for this study were Carisma(Kulzer, Germany), Tetric ceram(Ivoclar, Liechtenstein), Filtek Z250(3M, USA), and Arabesk Top(VOCO, Germany). Thirty disc-shaped specimens($10{\times}2mm$) were fabricated from each composite resin. Color changes of specimens after treatment using thermocycling system(KD-TCS30, Kwang-duk F.A. Korea) and after immersion in methylene blue(0.05% by Wt) were measured with colorimeter(Model Tc-6Fx, Tokyo Denshoku Co.) and obtained data were analyzed. Results and Conclusion: The results obtained from this study were as fo11ows. 1. The color change of Filtek Z250 was lesser than those of Tetric ceram and Arabesk Top after thermocycling (12000 times). 2. All of the composite resins in this study showed increase of color change according to increase of thermocycling frequency. 3. After treatment with methylene blue, the color change of Arabesk Top was greater than those of Carisma and Tetric ceram, and Tetric ceram was more stable than others.

• Carbon letters
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• v.26
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• pp.18-24
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• 2018

Pollution of chloride ion-reinforced concrete can trigger active corrosion processes that reduce the useful life of structures. Multifunctional materials used as a counter-electrode by electrochemical techniques have been used to rehabilitate contaminated concrete. Cement-based pastes added to carbonaceous material, fibers or dust, have been used as an anode in the non-destructive Electrochemical Chloride Extraction (ECE) technique. We studied the performance of the addition of Carbon Fiber (CF) in a cement-graphite powder base paste used as an anode in ECE of concretes contaminated with chlorides from the preparation of the mixture. The experimental parameters were: 2.3% of free chlorides, 21 days of ECE application, a Carbon Fiber Volume Fraction (CFVF) of 0.1, 0.3, 0.6, 0.9%, a lithium borate alkaline electrolyte, a current density of $4.0A/m^2$ and a cement/graphite ratio of 1.0 for the paste. The efficiency of the ECE in the traditional technique using metal mesh as an anode was 77.6% and for CFVF of 0.9% it was 90.4%, with a tendency to increase to higher percentages of the CFVF in the conductive cement-graphite paste, keeping the pH stable and achieving a homogeneous ECE in the mass of the concrete contaminated with chlorides.