• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.498-503
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• 2017

There is no unusual difference in the initial viscosity of the propellant applied with yellow iron oxide and red iron oxide. In addition, the thermal decomposition rate of the material added with yellow iron oxide is faster than that of the addition of red iron oxide. Especially, it was confirmed that the pressure exponent was 18% lower at high temperature and high pressure. The initial viscosity was lowest at 71% of large particle/small particle ratio

• Journal of the Korean Institute of Navigation
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• v.14 no.1
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• pp.21-38
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• 1990

This paper discusses the various modes of operations of cargo ships which are liner operations, tramp shipping and industrial operations, and mathematical programming, simulation , and heuristic method that can be used to solve ships routing and scheduling problems for each of these operations. In particular, this paper put emphasis on a crude oil tanker scheduling problem. The problem is to achieve an optimal sequence of cargoes or an optimal schedule for each ship in a given fleet during a given period. Each cargo is characterized by its type, size, loading and discharging ports, loading and discharging dates, cost, and revenue. Our approach is to enumerate all feasible candidate schedate schedules for each ship, where a candidate schedule specifies a set of cargoes that can be feasibly carried by a ship within the planning horizon , together with loading and discharging dates for each cargo in the set. Provided that candidate schedules have been generated for each ship, the problem of choosing from these an optimal schedule for each ship is formulated as a set partitioning problem, a set packing problem, and a integer generalized network problem respectively. We write the PASCAL programs for schedule generator and apply our approach to the crude oil tanker scheduling problem similar to a realistic system.

• Journal of Pharmaceutical Investigation
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• v.32 no.1
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• pp.41-45
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• 2002

The purpose of this study is to microencapsulate a highly hygroscopic drug, pyridostigmine bromide (PB), with a waterproof wall material, in order to increase the flowability of the drug particles. Polyvinylacetaldiethylaminoacetate (AEA), Eugragit E and Eugragit RS were examined as the wall materials. Microcapsules containing PB were prepared by the evaporation technique in an acetone/liquid paraffin system using aluminum tristearate as a core material, and evaluated for drug encapsulation efficiency, surface morphology, particle size and drug dissolution. The encapsulation of PB in the wall material was almost complete. Among the wall materials examined, AEA exhibited the most excellency in shape, surface texture, flowability, size distribution of microcapsules. Above results suggest that AEA would be a potential wall material for microcapsulation of highly hygroscopic drugs, such as PB. Through microencapsulation with AEA, inconvenience of handling of PB powders encountered in the process of weighing and packing the powders to tableting die or capsule body could be greatly improved.

• Geomechanics and Engineering
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• v.11 no.6
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• pp.805-820
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• 2016

A fully coupled non-linear effective stress response finite difference (FD) model is built to survey the counter-intuitive recent findings on the reliance of pore water pressure ratio on foundation contact pressure. Two alternative design scenarios for a benchmark problem are explored and contrasted in the light of construction emission rates using the EFFC-DFI methodology. A strain-hardening effective stress plasticity model is adopted to simulate the dynamic loading. A combination of input motions, contact pressure, initial vertical total pressure and distance to foundation centreline are employed, as model variables, to further investigate the control of permanent and variable actions on the residual pore pressure ratio. The model is verified against the Ghosh and Madabhushi high acceleration field test database. The outputs of this work are aimed to improve the current computer-aided seismic foundation design that relies on ground's packing state and consistency. The results confirm that on seismic excitation of shallow foundations, the likelihood of effective stress loss is greater in deeper depths and across free field. For the benchmark problem, adopting a shallow foundation system instead of piled foundation benefitted in a 75% less emission rate, a marked proportion of which is owed to reduced materials and haulage carbon cost.

• Bulletin of the Korean Chemical Society
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• v.12 no.2
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• pp.199-206
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• 1991

A statistical thermodynamic theory of thermotropic main-chain polymeric liquid crystalline melts is developed within the framework of the lattice model by a generalization of the well-known procedure of Flory and DiMarzio. According to the results of Vasilenko et al., the theory of orientational ordering in melts of polymers containing rigid and flexible segments in the main chain is taken into account. When the ordering of flexible segments in the nematic melt is correlated with that of rigid mesogenic groups, the former is assumed to be given as a function of the ordering of rigid mesogenic cores. A free energy density that includes short-range packing contributions is formulated. The properties of the liquid-crystalline transiton are investigated for various cases of the system. The results calculated in this paper show not only the order-parameter values but also the first-order phase transition phenomena that are similar to those observed experimentally for the thermotropic liquid-crystalline polymers and show the transitional entropy terms which actually increase upon orientational ordering. In the orientational ordering values, it is shown that mesogenic groups, flexible segments, and gauche energy (temperature) may be quite substantial. Finally, by using the flexibility term, we predict the highly anisotropic mesophase which was shown by Vasilenko et al.

• Journal of Surface Science and Engineering
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• v.54 no.3
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• pp.139-143
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• 2021

Cr-Al-N coatings were deposited onto WC-Co substrates using a cathodic arc evaporation (CAE) system. CAE technique is recognized to be a very useful process for hard coatings because it has many advantages such as high packing density and good adhesion to metallic substrates. In this study, the influence of deposition temperature as a key process parameter on film growth behavior and mechanical properties of Cr-Al-N coatings were systematically investigated and correlated with microstructural changes. From various analyses, the Cr-Al-N coatings prepared at deposition temperature of 450℃ in the CAE process showed excellent mechanical properties with higher deposition rate. The Cr-Al-N coatings with deposition temperature around 450℃ exhibited the highest hardness of about 35 GPa and elastic modulus of 442 GPa. The resistance to elastic strain to failure (H/E ratio) and the index of plastic deformation (H³/E² ratio) were also good values of 0.079 and 0.221 GPa, respectively, at the deposition temperature of 450℃. Based on the XRD, SEM and TEM analyses, the Cr-Al-N coatings exhibited a dense columnar structure with f.c.c. (Cr,Al)N multi-oriented phases in which crystallites showed irregular shapes (50~100nm in size) with many edge dislocations and lattice mismatches.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.48 no.1
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• pp.13-20
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• 2022

The lifetime incidence of epistaxis in dental and maxillofacial practice has been reported to be as high as 60% and can be caused by dental implant placement, Le Fort I osteotomy, intranasal supernumerary tooth, odontogenic tumors, blood disorders and maxillofacial trauma. Most epistaxis cases are minor and easily managed with direct compression on the nares for 10 minutes. For more significant or recurrent epistaxis, other techniques might include electrocautery, anterior or posterior nasal packing, or Foley catheter balloon. For patients with refractory epistaxis, cauterization of the sphenopalatine artery under endonasal endoscopy or embolization of the internal maxillary artery should be performed. Epistaxis control is required in patients diagnosed with inherited or acquired bleeding disorders or with drug-induced coagulopathies during dental procedures. In these cases, hemostatic system adjustment and hemostasis achieved by local and adjunctive methods are required. Dentists and maxillofacial surgeons must be aware that the nasal cavity is a potential source of perioperative hemorrhage. Depending on the invasiveness of the dental intervention, preoperative involvement of the hematologist and cardiologist is usually necessary to reverse anticoagulation or to cease anticoagulant therapy.

• Journal of muscle and joint health
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• v.30 no.3
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• pp.263-272
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• 2023

Purpose: The aim of this study was to provide a scientific basis for shelf life and re-establish the shelf life in a hospital environment by investigating the validity periods of various packaging materials. Methods: We selected six departments to store sterilized items, prepared 482 sterilized items, and stored them for 12 months. Each sample was tested using a microbiological culture in the laboratory every two weeks. When the result was positive, the sample was considered contaminated. The temperature and relative humidity were measured using an automatic control system to investigate the storage environment during the study period. Results: Except for two samples, which were positive in the 22nd and 28th weeks, 480 samples were negative. The temperature and relative humidity of the sample storage area were measured every week. The annual average temperature was 23.6±1.6℃, and the mean relative humidity was 35.1±15.2%. The cabinets used in this study were the two-open and four-closed types. Conclusion: This study confirmed the validity of the expiration date in a hospital environment. Based on the results, the nonwoven fabric remained sterile for more than nine months. No case of contamination of the paper-plastic pouch packaging was observed, owing to the microbial culture for two months.

• Applied Chemistry for Engineering
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• v.26 no.4
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• pp.495-504
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• 2015

This work investigated the characteristics of a packed-bed plasma reactor system and the performances of the plasma reactors connected in series or in parallel for the decomposition of ethylene. Before the discharge ignition, the effective capacitance of the ${\gamma}$-alumina packed-bed plasma reactor was larger than that of the reactor without any packing, but after the ignition the effective capacitance was similar to each other, regardless of the packing. The energy of electrons created by plasma depends mainly on the electric field intensity, and was not significantly affected by the gas composition in the range of 0~20% (v/v) oxygen (nitrogen : 80~100% (v/v)). Among the various reactive species generated by plasma, ground-state atomic oxygen and ozone are understood to be primarily involved in oxidation reactions, and as the electric field intensity increases, the amount of ground-state atomic oxygen relatively decreases while that of nitrogen atom increases. Even though there are many parameters affecting the performance of the plasma reactor such as a voltage, discharge power, gas flow rate and residence time, all parameters can be integrated into a single parameter, namely, specific input energy (SIE). It was experimentally confirmed that the performances of the plasma reactors connected in series or in parallel could be treated as a function of SIE alone, which simplifies the scale-up design procedure. Besides, the ethylene decomposition results can be predicted by the calculation using the rate constant expressed as a function of SIE.

• Korean journal of food and cookery science
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• v.27 no.1
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• pp.63-73
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• 2011

Cabbage (Baechu) Kimchi in its truncated form was placed in four different packing materials, Ny/PE/LLDP, OPP/AL/PE, PP and PET, and quality changes were observed during storage. Changes in pH and total acidity showed an x-shaped cross-curve as pH decreased and total acidity increased during storage. PP tray showed the slowest change at $5^{\circ}C$ with time. The pH was initially 6.25, but decreased to 4.12~4.16 at 20 days, and total acidity showed a 4 to 4.8-fold increase after 20 days of storage compared to the initial value. During storage at $5^{\circ}C$, total bacterial count and lactic acid bacterial count rapidly increased after 4 days. The total bacterial quantity decreased after a period of time and there were differences according to packaging material; OPP/AL/PE packaging showed the most dramatic decrease. Change in microbial count mostly followed a similar pattern to that of total acidity for all packaging materials. Changes in the color of Kimchi liquid, when examined by color index in $L{\cdot}b$/a form, rapidly decreased over time, similar to pH. Small Ny/PE/PP and OPP/AL/PE packages of Kimchi were examined for changes in free volume inside the packaging. After 13 days of storage at $5^{\circ}C$, the volume was 243 mL, but storage at $20^{\circ}C$ resulted in a volume of 372 mL, a more than 1.5-fold increase in free volume. There were changes in the quality characteristics of small package Kimchi according to storage temperature and packaging material, and large changes in pH, total acidity, and microbial count were evident upon storage at $5^{\circ}C$ for 8 days, which was the optimum palatability period. Mostly, PP treatment showed the slowest quality changes upon storage at $5^{\circ}C$. However, due to small package Kimchi's fast consumption system, the appropriate choice of packaging material must consider the product's turnover ratio. Further, the varieties of small package Kimchi should be diversified according to different consumer preferences by offering Kimchi with different maturity levels. Further, since the leading consumer base ranges in age from the teens to thirties, the development of various products targeting such consumers is necessary.