• Proceedings of the Korea Concrete Institute Conference
• /
• 1998.04a
• /
• pp.129-136
• /
• 1998

In this study, lightweight aggregates were developed to see the possible application as a structural uses. For the evaluation purpose, several testings were conducted to compare the physical characteristics between the controlled lightweight aggregates and other lightweight aggregates purchased from different sources. The tests included property changes of fresh concrete and strength characteristics of hardened concrete for both normal and high strength ranges. In addition, a experiment was performed to analyze the freezing and thawing resistance of new lightweight aggregate concrete against other lightweight aggregate concrete against other lightweight aggregate concretes with some experimental parameters such as lightweight aggregates, curing conditions, and water-cement ratio. The test showed that the new lightweight aggregate could be used structural components. Continuous study will be planned for future evaluations.

• Journal of the Korea Concrete Institute
• /
• v.28 no.4
• /
• pp.445-454
• /
• 2016

With the increase of decrepit facilities, construction waste increased to a certain level and now the increase is more or less stabilized. Yet construction waste still constitutes the largest portion of the overall wastes. Also, it is inevitable to spend a huge amount of the national budget due to the aggravating shortage of aggregate caused by prohibition on collection of natural aggregates as well as due to the damage to the land and environment caused by development of the sources of aggregates. As a countermeasure to the situation, the Ministry of Land, Infrastructure and Transport promulgated the quality standard for recycled aggregate to manage the usage of recycled aggregate according to its quality. But use of recycled aggregate for the purpose of high added value still remains nominal. Therefore, this research aims to study the applicability of recycled aggregate concrete as structural concrete by evaluating the quality improvement effects and the performance of the recycled aggregate concrete including recycled fine aggregate and recycled coarse aggregate that have undergone carbonation for 4 days and 14 days respectively in the condition of 60% RH, 20% $CO_2$ and $20^{\circ}C$ temperature, suggested for carbonation modifying from the advance research. The result shows carbonation modify contributed to quality improvement with 0.91% decrease in absorption rate for recycled fine aggregate and 0.7% decrease in absorption rate for recycled coarse aggregate. The physical properties and durability of the recycled aggregate made of aggregate modified by carbonation showed results similar to general concrete, which confirmed the possibility of applying the recycled aggregate made of recycled aggregate modified by carbonation to structural concrete.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2004.05a
• /
• pp.380-383
• /
• 2004

The coarse and fine aggregates that make up the majority of concrete are resources. But, the raw naturals that make up concrete are our earth's resources and there is not a replenishable stock. Also industrial waste and life waste leaped into a pollution source. Therefore, as construction continue, quarries are exhausted and new sources must be discovered. The purpose of this paper is to investigate an application of recycled coal ash plastics in the construction field. The study examined the physical and mechanical properties of recycled coal ash plastics aggregate. In the results, although the absorption and specific gravity of SLAs increases slightly as the fly ash content increases, the compressive strength and modulus of elastic of concrete made with SLAs remains relatively constant when mortar type and volume fraction are also held constant. These values are always lower than natural-weight aggregate concretes.

• Computers and Concrete
• /
• v.14 no.5
• /
• pp.547-561
• /
• 2014

Artificial neural networks (ANN) has been proven to be able to predict the compressive strength and elastic modulus of recycled aggregate concrete (RAC) made with recycled aggregates (RAs) from different sources. However, ANN is itself like a black box and the output from the model cannot generate an exact mathematical model that can be used for detailed analysis. So in this study, sensitivity analysis is conducted to further examine the influence of each selected factor on the output value of the models. This is not only conducive to the determination and selection of the more important factors affecting the results, but also can provide guidance for researchers in adjusting mix proportions appropriately when designing RAC based on the variation of these factors.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.4 no.2
• /
• pp.125-135
• /
• 2016

The objective of this paper is to provide integrated Korea industrial standards(KS) for concrete aggregates, which has been separately provided with ten kinds of KS, in order to improve the way of quality management of concrete aggregate and to prevent distribution of unsuitable aggregates. For the sequences of the paper, typical foreign standards related to concrete aggregates including ASTM for US, EN for EU, JIS for Japan are reviewed and compared to provide necessities and feasibilities of the paper. Based on the analysis above results, existing KS for concrete aggregates, which have been separately provided with ten kinds being lack of correlation between each KS is integrated to KS F 2526 "Aggregates for concrete" in this paper. By doing this, in terms of terminology, the expression of the aggregate, which has been currently classified into specified terminologies of aggregates depending on sources, manufacturing methods of each aggregates, is able to be integrated to single expression of the aggregate for concrete. It is believed that integrated KS presented herein provides more desirable way in terms of its better accessibility, easier revision and closer connection between each aggregate kinds.

• Journal of Microbiology and Biotechnology
• /
• v.7 no.1
• /
• pp.68-74
• /
• 1997

One hundred and eighty two lactic acid bacteria, isolated mainly from kimchi, including reference strains were examined for their ability to utilize 95 carbon sources. The test strains were assigned to 5 major, 1 minor and 12 single-membered clusters based on the $S_{SM}$, UPGMA algorithm (at similarity of $80{\%}$). These aggregate clusters were equivalent to the genus Leuconostoc (aggregate cluster M and N), the genus Lactobacillus (aggregate cluster Q and R), and the genera Lactobacillus and Leuconostoc (aggregate cluster O and P) according to the database of the Biolog system. This study demonstrates that rapid identification and classification of isolates originating from kimchi can be achieved on the basis of such carbon source utilization tests.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.29 no.7B
• /
• pp.711-721
• /
• 2004

To provide the end-to-end service differentiation for assured services, the random early demotion and promotion (REDP) marker in the edge router at each domain boundary monitors the aggregate flow of the incoming in-profile packets and demotes in-profile packets or promotes the previously demoted in-profile packets at the aggregate flow level according to the negotiated interdomain service level agreement (SLA). The REDP marker achieves UDP fairness in demoting and promoting packets through random and early marking decisions on packets. But, TCP fairness of the REDP marker is not obvious as fur UDP sources. In this paper, to improve TCP fairness of the REDP marker, we combine a dropper with the REDP marker. To make packet transmission rates of TCP flows more fair, at the aggregate flow level the combined dropper drops incoming excessive in-profile packets randomly with a constant probability when the token level in the leaky bucket stays In demotion region without incoming demoted in-profile packets. It performs a dropping in the demotion at a domain boundary only if there is no prior demotion. The concatenate dropping at multiple domains is avoided to manifest the effect of a dropping at a domain boundary on TCP fairness. We experiment with the REDP marker with the combined dropper using ns2 simulator for TCP sources. The simulation results show that the REDP marker with the combined dropper improves TCP fairness in demoting and promoting packets by generating fair demoted in-profile traffic compared to the REDP marker. The effectiveness of the selected drop probability is also investigated with showing its impact on the performance of the REDP marker with the combined dropper.

• ETRI Journal
• /
• v.38 no.4
• /
• pp.746-756
• /
• 2016

Owing to the intermittent power generation of renewable energy sources (RESs), future wireless cellular networks are required to reliably aggregate power from retailers. In this paper, we propose a distributed power allocation (DPA) scheme for base stations (BSs) powered by retailers with heterogeneous RESs in order to deal with the unreliable power supply (UPS) problem. The goal of the proposed DPA scheme is to maximize our well-defined utility, which consists of power satisfaction and unit power costs including added costs as a non-subscriber, based on linear and quadratic cost models. To determine the optimal amount of DPA, we apply dual decomposition, which separates the master problem into sub-problems. Optimal power allocation from each retailer can be obtained by iteratively coordinating between the BSs and retailers. Finally, through a mathematical analysis, we show that the proposed DPA can overcome the UPS for BSs powered from heterogeneous RESs.

• Advances in materials Research
• /
• v.11 no.2
• /
• pp.147-164
• /
• 2022

This study aims to investigate the influence of scoria aggregate (SA) and silica fume (SF) as a replacement of conventional aggregate and ordinary Portland cement (OPC), respectively. Three types of concrete were prepared namely normal weight concrete (NWC) using limestone aggregate (LSA) and OPC (control specimen), lightweight concrete (LWC) using SA and OPC, and LWC using SA and partial SF (SLWC). The representative workability and compressive strength properties of the developed concrete were evaluated, and the results were correlated with non-destructive ultrasonic pulse velocity and Schmidt hammer tests. The LWC and SLWC yielded compressive strength of around 30 MPa and 33 MPa (i.e., 78-86% of control specimens), respectively. The findings indicate that scoria can be beneficially utilized in the development of structural lightweight concrete. Present renewable sources of aggregate will preserve the natural resources for next generation. The newly produced eco-friendly construction material is intended to break price barriers in all markets and draw attraction of incorporating scoria based light weight construction in Saudi Arabia and GCC countries. Findings of the SWOT analysis indicate that high logistics costs for distributing the aggregates across different regions in Saudi Arabia and clients' resistant to change are among the major obstacles to the commercialized production and utilization of lightweight concrete as green construction material. The findings further revealed that huge scoria deposits in Saudi Arabia, and the potential decrease in density self-weight of structural elements are the major drivers and enablers for promoting the adoption of lightweight concrete as alternative green construction material in the construction sector.

• Journal of Korean Society of Industrial and Systems Engineering
• /
• v.8 no.11
• /
• pp.57-68
• /
• 1985

Theories of capital have historically been amongst the most fertile sources of economic controversy. Many aspects of the modern debate, if not the techniques employed in its exposition, would have been as familiar to Marx, Ricardo, Bohm-Bawerk or Wicksell as to any present-day Cambridge economist. That conotroversies should arise in the course of theorizing cm the concept of capital and the function of profit is not surprising: that these debates have been so vigorous and virluent cannot be divorced from the general ideological and specific implications associated with the theories. In the context of a textbook on the theories of economic growth, the central question associated with capital that must he faced is whether the existence in the real world of heterogeneous capital goods inevitably invalidate; the conclusions of simple theories of "parables" which incorporate no more than a conception of a single, malleable, capital good. All the Cambridge writers have, to a greater or lesser extent, been concerned to deny that any unit can be found in which heterogeneous capital goods can be aggregated so as to simultaneously satisfy the pair of neoclassical requirements described above. Some of them have been more prepared than others to countenance such a possibility or, for practical purposes, to use some concept of aggregate capital in their models, but they are all deeply suspicious of attempts to use aggregate production function, incorporating aggregate "capital", so as to explain the flow of output, relative factor prices and the distribution of income.tribution of income.