• Resources Recycling
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• v.9 no.6
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• pp.15-22
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• 2000

There are many intensive efforts to develop the recycling technologies of waste plastics in steel works to tackle the saving of resources and the protection of the natural environment. In this study, the thermogravimetric analyses for three kinds of plastics, the combustion experiments and the theoretical approach for calculating the flame temperature in the blast furnace had been performed to understand the behavior of plastics in the raceway. The thermal decompositions of plastics were studied using thermogravimetric analyzer under the atmospheric condition. The starting temperature of thermal decomposition and the maximum weight loss point were increased in proportion to the logarithmic values of heating rate. The combustion characteristics of plastics were simulated in a coke-bed combustor. The combustion efficiency of plastics was lower than that of pulverized coal. The oxygen enrichment was found out to be one of the useful methods to increase the combustibility of plastics in raceway. The maximum injection rate of plastics was calculated based on the flame temperature.

• Resources Recycling
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• v.29 no.4
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• pp.31-44
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• 2020

Recently, plastic recycling has emerged as a social issue, and its importance is increasing. Therefore, this article reviewed the current status and the future directions of domestic plastic recycling. Plastic recycling is major economic and social problems not only in South Korea but also worldwide and is being treated as an important factor for protecting the environment and for sustainability in the next generation. In particular, China, which has been dealing with a large amount of plastic waste generated around the world, has banned importing plastic waste, therefore, other countries have faced the problem of recycling plastics in their countries. In South Korea, the landfill and incineration of the waste are becoming more difficult by the Framework Act on Resources Circulation, therefore, the recycling and reuse of plastics are a very important.

• Journal of Digital Convergence
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• v.19 no.10
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• pp.377-382
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• 2021

A fuzzy relation between X and Y as fuzzy subset of X × Y was proposed by Zadeh. Subsequently, several researchers have applied the notion of fuzzy subsets to various branches of mathematics and computer sciences. Murali an Nemitz have studied fuzzy relations connected with fuzzy equivalence relations and fuzzy functions. Ounalli and Jaoua defined a fuzzy difunctional relation on a set. difunctional relations are versatile mathematical tool, which can be used in software design and in database theory. Their work have revealed the usefulness of difunctional relations in program specification and in defining program correctness. The main goal of this paper is to define a fuzzy deterministic relation on a set, characterize the fuzzy deterministic relation as its level subsets and investigate some properties in connection with fuzzy deterministic relation. In particular we prove that a fuzzy relation R is fuzzy deterministic iff R is a fuzzy function.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.24 no.3
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• pp.131-140
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• 2018

As global environmental problems become more serious, bio plastic suppliers in developed countries are expected to drive demand for eco friendly packaging materials due to recycling regulations and consumer's attention. To catch up with this demand, various types of bio plastics have been introduced using plants such as corn and domestic companies are increasingly interested in this. Industrial interest in bio plastics is increasing to solve the recent environmental problems. The critical disadvantages of the weak mechanical strength and expensive product cost were gradually solved by extensive researches. In order to promote the active use of bio plastics, countries around the world are operation certification marks and standard systems. In this article, we have summarized recent trends in domestic and overseas bio plastics regulations, certification marks and identification labels.

• Journal of Aerospace System Engineering
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• v.14 no.1
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• pp.21-27
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• 2020

Aircraft should be equipped with various external stores for mission performance. Since these external stores may cause structural instability of aircraft, an evaluation of the effects between the aircraft and the external stores is required. For this purpose, an aircraft dynamic characteristics analysis reflecting an external store was performed, and the finite element model for the analysis of aircraft dynamic characteristics should simulate the dynamic characteristics of the component as accurately as possible while using a minimum of the nodes and elements. In this study, a stick model was constructed for dynamic characteristics analysis of the external fuel tank and installation pylon using MSC Patran/Nastran. For the calculation of the equivalent stiffness of the stick model, a simple beam theory was applied to construct the stick model of each part, and the validity of each stick models was confirmed by mode comparison with the fine model. Additionally, the model analysis of the stick model assembly, simulating a pylon equipped with an external fuel tank was performed to confirm that the basic modes required for the analysis of aircraft dynamic characteristics are well extracted. Finally, it was confirmed that the developed stick model assembly could be used for analysis of aircraft dynamic characteristics by comparing the errors in modes between the fine model assembly and the stick model assembly.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 2002.05a
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• pp.46-48
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• 2002

본 연구는 신문지 고지의 점착성 이물질 중 Primary Stickies의 정 량에 관한 것으로 서, 실제 신문지료를 화상분석하여 실시간으로 매크로크기의 점착성 이물질올 측정할 때 효율적인 측정조건을 탐색하여 제지공정의 l 현장에서 일차 점착성 이물질을 정량 하는 새로운 측정기의 측정 기준을 제시하고자 하였다. 이물질이란 제지공정에 의도적으로 첨가되지 않은 불질의 총칭으로 dirt 및 각종 점착 성 이물질 즉, stickies를 들 수 있다. 이 가운데 스틱키{stickies}란 부드럽고, 점착성을 나타내는 이물질의 총청으로 주로 점착제와 확스에 의해 형성된다. 스틱키는 고지 재활 용의 효율성을 가장 크게 저해하는 이물질로 와이어, 펠트 및 기타 공정요소에 부착되 어 초지 시 지절을 발생시킴으로써 생산성을 저하시킬 뿐 아니라, 외관상 상품가치와 인쇄적성올 저하시키며, 최종 제품의 강도적 물성 및 가공적성에도 영향을 미친다. 특 히 국내에서는 원가절감을 위해 고지의 재활용율올 증대시키고자 전력을 다하고 있으 며 환경보호 및 용수 절감올 위해 공정수를 절감하고 궁극적으로는 무방류화를 목표로 하고 있어 토지 계 내의 점착성 이물질의 투입과 농축 현상이 심각하게 진행되고 있는 실정이다. 초지공정에서 발생하는 스틱키 즉 점착성 이물질은 미세한 스크린의 슬롯 폭인 0.15 - -0.3mm 이상의 크기를 가져 스크린에 의해 분리될 수 있는 매크로 스틱키{macro s stickies}와 이보다 작은 마이크로 스틱키(micro stickies)로 크게 분류된다. 즉 매크로 스틱키는 스크린에 의해 분리될 수 있으나 마이크로 스틱키는 스크린을 통하여 기계적 으로 분리할 수 없다는 문제점을 지니고 있다. 스틱키는 또 거동 특성에 따라 primary s stickies와 secondary stickies로 구분할 수 있다. primary stickies는 펄핑과정에서 점착 성 이물질이 파괴됨에 따라 나타나지만, secondary stickies는 지류 제지공정의 백수에 용해 되거나 분산된 상태인 1때1 이하의 콜로이 드로 폰재 한다. 이 러 한 secondary stickies 는 pH, 온도의 변화나 각종의 첨가제에 의해 웅집이나 홉착 등을 발생할 수 있는 잠재 적 문제점 등을 가지고 있다. 예를 들어 양성 고분자의 첨가는 펄프 섬유를 웅집시킬 뿐 아니라 지료에 함유된 secondary dtickies의 안정성을 저하시켜 응집, 침적시키는 작용을 한다. 따라서 분리가 어렵고, 제지공정에서 문제를 일으키기 쉬운 2차 스퇴키를 적절히 제어하기 위한 기술 개발은 용수절감 뿐 아니라, 초지공정의 침적물 절감을 통 한 공정개선에도 매우 중요한 요소기술이라 할 수 있다.

• Journal of the Korea Organic Resources Recycling Association
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• v.10 no.1
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• pp.109-119
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• 2002

This study is to estimate that food waste bags with biodegradable plastic are really decomposed by microorganism in composting with food waste and to examinate how biodegradable plastic affects composting. 6 kinds of 30%, 4 kinds of 100% and 2 kinds of none biodegradable plastics were used in d1is study. In 30% biodegradable plastics the highest Degradation rare is 6% in meso-condition and 10% in thermal-condition. Srain at auto break decreased to 150% in meso-condition and 120% in thermal-condition. Stress at max load were also reduced to $180kgf/cm^2$ in mesocondition and $200kgf/cm^2$ in thermal-condition. Usually, LLDPE decreased larger than HDPE in physical characreristics but HDPE is higher in degradation rate. 1n stain at auto break and stress ar max load 100% biodegradable plastic declined to 230% and to $380kgf/cm^2$ in meso-condition and to 440% and to $400/cm^2$ in thermal-condition respectively. 100% biodegradable plastics showed higher biodegradation and decomposition then 30%. They appeared clearly through SEM observation. As a result, it was not appropriate to use 30% biodegradable plastics as food waste bag because they were not decomposed perfectly. It is possible to use 100% biodegradable plastic as it but cost is too high. So development of technique is needed.

• Journal of the Korean Institute of Intelligent Systems
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• v.26 no.5
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• pp.416-422
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• 2016

Lots of plastics are widely used in a variety of industrial field. And the amount of plastic waste is massively produced. In the study of waste recycling, it is emerged as an important issue to prevent the waste of potentially useful resource materials as well as to reduce ecological damage. So, the recycling of plastic waste has been currently paid attention to from the view point of reuse. Existing automatic sorting system consist of near infrared ray (NIR) sensors to classify the types of plastics. But the classification of black plastics still remains a challenge. Black plastics which contains carbon black are not almost classified by NIR because of the characteristic of the light absorption of black plastics. This study is focused on handling how to identify black plastics instead of NIR. Raman spectroscopy is used to get qualitative as well as quantitative analysis of black plastics. In order to improve the performance of identification, Support Vector Machine(SVM) classifier and Principal Component Analysis(PCA) are exploited to more preferably classify some kinds of the black plastics, and to analyze the characteristic of each data.

• Resources Recycling
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• v.26 no.6
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• pp.73-83
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• 2017

Used small household appliances have a wide variety of product types and component materials, and contain high percentage of black plastics. However, they are not being recycled efficiently as conventional sensors such as near-infrared ray (NIR), etc. are not able to detect black plastic by types. In the present study, an automatic sorting system was developed based on laser-induced breakdown spectroscopy (LIBS) to promote the recycling of waste plastics. The system we developed mainly consists of sample feeder, automatic position recognition system, LIBS device, separator and control unit. By applying laser pulse on the target sample, characteristic spectral data can be obtained and analyzed by using CCD detectors. The obtained data was then treated by using a classifier, which was developed based on artificial intelligent algorithm. The separation tests on waste plastics also were carried out by using a lab-scale automatic sorting system and the test results will be discussed. The classification rate of the radial basis neural network (RBFNNs) classifier developed in this study was about > 97%. The recognition rate of the black plastic by types with the automatic sorting system was more than 94.0% and the sorting efficiency was more than 80.0%. Automatic sorting system based on LIBS technology is in its infant stage and it has a high potential for utilization in and outside Korea due to its excellent economic efficiency.

• Archives of design research
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• v.19 no.2 s.64
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• pp.283-292
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• 2006

The Plastic material had been developed in the middle of the 19th century as an alternative material. Along with the development of the electrical engineering industry, it cropped up into center stage as an effective material and has increasingly expanded its use. As such, the plastic material has bound deep-seated ties with the design activities of industrial products, coming into the main material for a variety of industrial designs. Despite its dose affinity to design function in terms of its materialistic property, we have rarely seen examples of intensive study on the realtionship between plastics and designs. This study aims to find the importance that the substance affects industrial products in designs along with the development of plastic materials. With the objective in mind, we made a review of the streamline stylishness that had flourished in the twenties and thirties of the 19th century. Through this study, we understand that the plastic material has a close realtionshop with design activities in three different aspects. First, its amorphous state of nature makes it possible to change into any shape one desires in plastic surgery, which feature in turn influences the moulding of any design forms. Second, the plastic material is best suited to mass-manufacture, which induces to reduce the cost of production. Hence, the expansion of design industry. Third, the plastic material allows the multiple variety of colors, sensitivity, gloss and patterns and infinitely large possibility ranging from natural senses to human senses with the result that numberless diversity of designs cdould come into being.