• Resources Recycling
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• v.32 no.3
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• pp.3-8
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• 2023

This study discussed production, demand, and future prospects of rubidium, which is an alkali group metal that is highly reactive to various media and requires carefulness in handling, but no significant environmental hazard of rubidium has been reported yet. Rubidium is used in various fields such as optoelectronic equipment, biomedical, and chemical industries. Because of difficulty in production as well as limited demand, the transaction price of rubidium is relatively high, but its detail information such as market status and potential growth is uncertain. However, if the mass production of versatile ultra-high-performance equipment such as quantum computers and the necessity of rubidium use in the equipment are confirmed, there is a possibility that the rubidium market will expand in the future. Rubidium is often found together with lithium, beryllium, and cesium, and may be present in granite containing minerals such as lepidolite and pollucite, as well as in seawater and industrial waste. Several technologies such as acid leaching, roasting, solvent extraction, and adsorption are used to recover rubidium. The maximum recovery efficiency of the rubidium from the sources and the processing above is generally high, but, in many practices, rubidium is not the main recovery target, and therefore the actual recovery effects should depend on presence of other valuable components or impurities, together with recovery costs, energy consumption, environmental issues, etc. In conclusion, although the current production and consumption of rubidium are limited, with consideration of the possible market fluctuations according to the emergence of large-scale demand sources, etc., further investigations by related institutions should be necessary.

• Journal of the Korea Concrete Institute
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• v.18 no.2 s.92
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• pp.199-204
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• 2006

Recently, The sludge water of ready mixed concrete has been investigated because of environmental pollution and disposal cost. So, sludge water is partially reused as mixing water. However, if sludge water is reused too much that would influence the qualify of concrete. KS specification limits the amount of sludge content up to 3% of cement weight. In this study, the effect of ready mixed concrete sludge on the characteristics of concrete is compared to raise the reuse ratio of sludge of ready mixed concrete. According to this experiment results, as blending ratio of re-mi-con sludge increases, workability is decreases. However, the sludge of ready mixed concrete water have a positive effect on the strength development. The drying shrinkage and the resistance of freezing and thawing have a minor effect.

• Journal of the Korea Society of Computer and Information
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• v.14 no.7
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• pp.161-168
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• 2009

In this paper, we studied about an consolidated transportation model to transport EOL (end-of-life) electronic household appliances for recycling in South Korea. The objective is to minimize the total traveling distance of the vehicles transporting EOL electronic household appliances collected by local authorities and major manufacturers' distribution centers to assigned R/C(recycling center) in South Korea. Current reverse logistics for recycling EOL electronic household appliances is operated by local authorities and major manufacturers individually, and it is inefficient for the following reasons: excessive traveling distance, transportation cost, low truck capacity utilization, and so on. The presented model is developed to solve this problem. We apply a integer programming to solve this problem and present computational results using actual field data.

• Applied Biological Chemistry
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• v.35 no.2
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• pp.115-121
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• 1992

Avermectin B1(abamectin) is an very effective acaricide/insecticide. Because it is applied at low rates, the resultant residue level would be quite low and this requires highly sensitive analytical method. In this study, three analytical methods for avermectin $B1_a$, were compared in view of detectability and sensitivity. The first analytical method was an HPLC method employing the fluorescence detection of avermectin. The second analytical technique to quantitate avermectin $B1_a$, and its photodegradative delta 8,9-isomer employed trifluoroacetic anhydride and 1-methylimidazole in DMF. The new method was the modification of trifluorescence method. The average recoveries of avermectin $B1_a$ for the concentration range from 1 and 10 ng/g in whole apple fruit by fluorescence method were 90.3% and 88.2% respectively. In trifluorescence method, the recoveries of the avermectin $B1_a$ and delta 8,9-isomer were 100.7% and 94.7% in concentration from 5 ng/g and 25 ng/g. The average recoveries of 5 ng and 25 ng/g in the newly modified method were 95.0, 99.0. 96.0, 92.8% in whole apple and soil respectively.

• Journal of Hydrogen and New Energy
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• v.17 no.1
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• pp.98-108
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• 2006

본 연구에서는 이 단계 연속 바이오 수소/메탄 생산공정의 경제성을 조사하였다. 경제적 관점에서 다양한 수소 및 메탄 발효용 생물반응기를 비교 평가하였다. 이를 바탕으로 포도당으로부터 일 단계 수소발효를 위해 고온 trickling biofilter 반응기 (TBR, $100\;m^3$ 규모)를, 일 단계 반응의 부산물로 생성된 유기산과 알콜류의 이 단계 메탄전환을 위해 고온 upflow anaerobic sludge 반응기 (UASB; $700\;m^3$ 규모)를 선정하였다. 본 이 단계 공정의 수소생산 비용은 $$\;0.26/Nm^3$으로 계산되었고, 이는 고온 TBR 반응기만을 이용한 경우보다 약 30 % 낮았다. 이 단계 공정의 낮은 수소생산 비용은 높은 에너지 회수율과 낮은 슬러지 처리비용에 의한 것이었다. 생물학적 수소 생산공정의 경제성은 탄소원의 종류, 생물반응기의 형태 등 여러 인자에 의해 변경될 수 있으나, 본 연구결과는 향후 연구를 위한 유용한 기준으로 고려될 수 있다.

• The Journal of Society for e-Business Studies
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• v.11 no.1
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• pp.91-112
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• 2006

Unlike typical corporate investments, IT expenditures have direct impact on many aspects of a business, including those that are difficult to quantify. Therefore, financial indicators alone do not do justice to the full effect of an If investment. Proposed in this paper is a methodology to measure the return on IT investments, including non-financial impacts expressed in terms of monetary values. This methodology shows tangible cost as well as hidden cost by analyzing total cost of ownership. The methodology also produces ROI by performing cost benefit analysis including financial and non-financial factors. This paper suggests a more objective validation of If's impact on the business activities. It rationalizes investment priorities and provides a systematic approach to effective IT investment.

• The Journal of Society for e-Business Studies
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• v.11 no.1
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• pp.53-67
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• 2006

It is difficult to justify an IT investment unless the investment is expected to have a direct impact on a corporation's performance under rapidly changing business environment. It is important to demonstrate the benefit of the investment through a pre-investment assessment process to induce the executive's decision. This paper presents a methodology to assess the investment by analyzing cost and benefit of the investment. This methodology shows tangible cost as well as hidden cost by analyzing total cost of ownership. The methodology also produces ROI by performing cost benefit analysis including financial and non-financial factors. This paper suggests a systematic way to support If investment decision marking process by evaluating the investment objectively.

• Mineral and Industry
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• v.28
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• pp.1-13
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• 2015

In this study, it was carried out separation process research and development to be able to produce high-grade tungsten concentrate form tungsten taken form Mongolia. In order to reduce treatment cost and increase separation efficiency the jig separation at first was applied for recovering the concentrate. Which reground would make the degree of liberation increase. Which was treated by shaking table to reject the gangue minerals from the first concentrate. Because the heavier product contains not only ferberite but also cassiterite, the product was treated by further dry magnetic separation to obtain the ferberite concentrate. Finally, the high-grade ferberite concentrate of 67.63% $WO_3$ could be obtained with recovery of 86.07% through the separation process developed in this study.

• Journal of Energy Engineering
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• v.11 no.3
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• pp.210-215
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• 2002

In respect of global environment protection and efficient utilization of energy, co-generation systems, which have greatly higher efficiency than the other generations, have been developed and put to practical use. Assuming that the co-generation system would be operating in Park Hotel, this paper calculates the difference between the heat and electricity rates by the conventional method and the co-generation system, considers the cost of new investment and analyzes introduction economics based on the return on investment. The introduction is turned out to be recommendable, since the return of investment for co-gen oration equipment is about ten years when the co-generation profits in heat and electricity rate. Additionally, accounting for interest rate drop, improvement of environmental matters or electricity rate increase, it is shown to be even more economical.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.16 no.4
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• pp.92-100
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• 2002

In respect of global environment protection and efficient utilization of energy, co-generation systems, which have greatly higher efficiency than the other generations, have been developed and put to practical use. Assuming that the co-generation system would be operating in H-Department of Kwang-ju city, this paper calculates the difference between the heat and electricity rates by the conventional method and the co-generation system considers the cost of new investment and analyzes introduction economics based on the return on investment. The introduction is turned out to be recommendable, since the return of investment for co-generation equipment is about five years when the co-generation profits in heat and electricity rate. Additionally, accounting for interest rate drop, improvement of environmental matters or electricity rate increase, it is shown to be even more economical.