• Journal of the Korean Operations Research and Management Science Society
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• v.16 no.1
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• pp.76-88
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• 1991

Stochastic convexity (concavity) of a stochastic process is a very useful concept for various stochastic optimization problems. In this study we first establish stochastic convexity of a certain class of Markov additive processes through probabilistic construction based on the sample path approach. A Markov additive process is abtained by integrating a functional of the underlying Markov process with respect to time, and its stochastic convexity can be utilized to provide efficient methods for optimal design or optimal operation schedule wide range of stochastic systems. We also clarify the conditions for stochastic monotonicity of the Markov process. From the result it is shown that stachstic convexity can be used for the analysis of probabilitic models based on birth and death processes, which have very wide applications area. Finally we demonstrate the validity and usefulness of the theoretical results by developing efficient methods for the optimal replacement scheduling based on the stochastic convexity property.

• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.3
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• pp.330-337
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• 2021

3D printing is not only at the fundamental study and small-scale level, but has recently been producing buildings that can be inhabited by people. Buildings require a lot of cost and labor to work on the form work, but if 3D printing is applied to the building, the construction industry is received attention from technologies using 3D printing as it can reduce the construction period and cost. 3D printing technology for buildings can be divided into structural and non-structural materials, of which 3D printing is applied to non-structural materials. Because 3D printing needs to be additive manufacturing, control such as curing speed and workability is needed. Since cement mortar has a large shrinkage due to evaporation of water, cement polymer dispersion is used to improve the hardening speed, workability, and adhesion strength. The addition of polymer dispersion to cement mortar improves the tensile strength and brittleness between the cement hydrate and the polymer film. Cement mortar using polymer materials can be additive manufacturing but it has limited height that can be additive manufacturing due to its high density. When light-weight materials are mixed with polymer cement mortar, the density of polymer cement mortar is lowered and the height of additive manufacturing, so it is essential to use light-weight materials. However, the use of EVA redispersible polymer powder and light-weight materials, additional damage such as cracks in cement mortar can occur at high temperatures such as fires. This study produced a test specimen incorporating light-weight materials and EVA redispersible polymer powder to produce exterior building materials using 3D printing, and examined flame resistance performance through water absorption rate, length change rate, and cone calorimeter test and non-flammable test. From the test result, the test specimen using silica sand and light-weight aggregate showed good flame resistance performance, and if the EVA redispersible polymer powder is applied below 5%, it shows good flame resistance performance.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2014.11a
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• pp.47-48
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• 2014

This study is to hydration property of low carbon type recycled cement from waste cementitious powder and cement raw materials. Waste cementitious powder possible to low carbon type recycled cement in small part of additive materials. Also, low carbon type recycled cement using waste cementitious powder is suitable for low heat type cement.

• Plant Journal
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• v.10 no.1
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• pp.34-39
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• 2014

Simulation works for comparing removal capabilities of acid gases contained in natural gas among several aqueous amine absorbents using commercial process simulator PROMAX(BR&E Co.) were carried out. Amine aqueous solution used in this study were 30 wt% MEA, 30 wt% DEA, 50 wt% MDEA, and 50 wt% MDEA with 3 wt% piperazine as additive. We obtained the simulated results that while MEA aqueous solution is relatively capable of more $CO_2$ gas, but DEA, MDEA, MDEA aqueous solutions with piperazine as additive are capable of more $H_2S$ gas. Also, we found that 30 wt% MDA aqueous solution is the smallest circulate rate of lean amine solution, and 50 wt% MDEA aqueous solution with 3 wt% piperazine as additive is the smallest heat duty in stripping unit. 50 wt% MDEA aqueous solution with 3 wt% piperazine as additive is found less amine circulation rate than 50 wt% MDEA due to the introduction of additive.

• Cross-Cultural Studies
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• v.46
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• pp.143-171
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• 2017

In this paper, we present a morphosyntactic and semantic study of the concessive conjunctive phrase [todavía que] in the Andean and River Plate areas of Latin America. Real Academia $Espa{\tilde{n}}ola$(2009) describes that the adverb todavía occurs in a variety of focus-sensitive environments and specially, in the Andean and River Plate areas, the phrase [todavía que] participates in the concessive constructions and triggers an additive interpretation. It is well known that the Quechuan suffix '-raq' and the Aymaran suffix '-raki' have the meaning of todavía which is characterized as a additive particle. Due to the absence of the paratactic relationship between the mentioned Spanish adverb and those indigenous suffixes, the adverb todavía in [todavía que] is used as a additive focalizer. We assume that these morphosyntactic and semantic properties are derived from the language contact of Quechua-Spanish and Aymara Spanish. Based on this assumption, we will further assume that the etymological peculiarity of todavía as a universal quantifier is closely related to the reading of [todavía que] as a Scalar Additive Concessive Conjunctive Phrase.

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.4
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• pp.106-113
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• 2010

We were tried to draw a conclusions related to additive amount of gypsum in blast furnace slag in the study. In the result, fluidity of concrete decreased with an increase of gypsum and was not satisfied with KS standard in the cases of natural gypsum and limestone sludge more than 2.6% addition. Early compressive strength of concrete containing desulfurized gypsum, fluosilicic acid gypsum and phosphoric acid gypsum were improved respectively but calcined lime sludge and lime powder were not influenced on strength. If available, additive gypsum should be managed less than 2.0% owing to low fluidity. In low temperature, fluosilicic acid gypsum was to advantages on the fluidity while desulfurized gypsum was in high temperature. There also are conclusions that additive gypsum was to be 2.6% in winter and in summer; it's to be fewer than 2.6%.

• Resources Recycling
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• v.27 no.1
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• pp.3-13
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• 2018

3D printing, also known as Additive Manufacturing (AM), is being positioned as a new business model of revolutionizing paradigms of existing industries. Launched in early 2000, 3D printing technology for architecture has also advanced rapidly in association with machinery and electronics technologies mostly in the United States and Europe. However, 3D printing systems for architecture require different mechanical characteristics from those of cement/concrete raw materials used in existing construction methods. Accordingly, in order to increase utilization of raw materials produced in the cement and resource recycling industry, it is necessary to develop materials processing and utilization technology, to secure new property evaluation and testing methods, and to secure database related to environmental stability for a long period which aims to reflect characteristics of an architectural 3D printing technology.

• Advances in concrete construction
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• v.9 no.1
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• pp.93-102
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• 2020

In this study, we examined the relationship among the rheological properties, workability, and extrudability in the construction of concrete structures using additive manufacturing. We altered the component materials (binder type, water-binder (W/B) ratio, sand ratio) to assess their effect on the rheological properties experimentally. The results indicated that the W/B and sand ratios had the largest effect on the rheological properties. In particular, when the sand ratio increased, it indicated that adjusting the sand ratio would facilitate control over the rheological properties. Additionally, we compared the rheological properties with the results of a traditional workability evaluation, namely the table flow test. This indicated the possibility of inferring the rheological properties by using traditional methods. Finally, we evaluated extrusion quantity according to table flow. The extrusion rate was 350 g/s for a flow of 210 mm and 170 g/s for a flow of 130 mm, indicating that extrusion rate increased as flow increased; however, we concluded that a flow standard of approximately 140-160 mm is suitable for controlling the actual extrusion quantity and rate.

• Journal of the Korea Institute of Building Construction
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• v.7 no.4
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• pp.139-144
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• 2007

The purpose of this study is to analyze concrete characteristics by admixing agent and additive contents according to the change of unit-water to identify its effect on compressive strength. First of all, as for flesh concrete, overall unit-water showed a tendency to decrease as component inclusion rate of admixing agent was increased. In addition, air content showed a tendency to increase by increasing WR, WB, NP series admixing agent contents, on the other hand, the change of air content was gentle by around $1.5{\pm}0.5%$ for S, T, M series agents. Bulk density showed an inverse proportion to the change of air content. As for hardened concrete, expression rate of 3-day age compressive strength was generally decreased for S, T, WR, WB, NP, M series admixing agent component. Also, expression rate of 7-day age compressive strength showed an excellent record for S, M series agents, and expression rate of 28-day age compressive strength showed a tendency to increase more than plain on the whole.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.1051-1060
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• 2008

The use of the coal ash for surcharge material, in a view of the environmental aspect, can decrease amount of the reclamation through recycling waste materials as well as prevent a destruction of the ecosystem attributed to sand picking. In addition, it can reduce both unit cost of material and construction expenses. In this study, new construction material as alternative surcharge material using coal ash, which is by-product from thermoelectric power plant, were developed. Mixing ratios of fly ash and bottom ash derived from the coal ash in Samchunpo thermoelectric power plants were determined. Furthermore, mixing conditions depending on the ratios of the cement and gypsum used for chemical additive were determined too. Uniaxial compression strength tests were conducted at different mixing conditions and Design graph of optimum mixing ratio at each required strength for economic efficiency is indicated in this paper.