Earticle

A sewage treatment plant built with water plants and gravels in an open field has been operated for 3 years with a daily average flow of 50 m3. The quality of treated water was regularly analysed and the economic assesment of the process has been investigated. Seasonal performance of the plant has been investigated with emphasis on treatment efficiency, shock loading responses, effects of sewage evaporation rate, effects of high and low ambient temperature, long term shutdown and start-up. Analyses of sewage indicated that the quality and quantity of the sewage generated in farming and fishing villages depend mainly on the life pattern of the residents. A sewage treatment plant with mechanical equipments may have high operating costs and low treatment efficiency to treat this type of sewage.However, the sewage treatment plant suggested in this study employs natural purification processes and has showed stable long term treatment efficiency even with shock loading and ambient temperature variation. Treatment of phosphorus with mechanical processes may need high operating costs but the suggested processes using water plants and gravels removes phosphorus in natural ways resulting in high removal efficiency and low costs. The natural sewage treatment plant showed good efficiency for all year around to meet the discharge guide-lines of drinking water protection area with respect to BOD, COD, TN. TP and SS. The high treatment efficiency may be due to the action of microorganisms living attached on the surface of the gravels. However, the water plants showed limited treatment performance.

A liquid metal reactor (LMR) operated at high temperatures is subjected to both cyclic mechanical loading and thermal loading; thus, creep-fatigue is a major concern to be addressed with regard to maintaining structural integrity. The Korea Advanced Liquid Metal Reactor (KALIMER), which has a normal operating temperature of $545^{\circ}C$ and a total service life time of 60 years, is composed of various cylindrical structures, such as the reactor vessel and the reactor baffle. This study focuses on the creepfatigue crack initiation for a cylindrical Y-junction structure made of 316 stainless steel (SS), which is subjected to cyclic axial tensile loading and thermal loading at a high-temperature hold time of $545^{\circ}C$. The evaluation of the considered creep-fatigue crack initiation was carried out utilizing the ${\sigma}_d$ approach of the RCC-MR A16 guide, which is the high-temperature defect assessment procedure. This procedure is based on the total accumulated strain during the service time. To confirm the evaluated result, a high-temperature creep-fatigue structural test was performed. The test model had a circumferential through wall defect at the center of the model. The defect front of the test model was investigated after the $100^{th}$ cycle of the testing by utilizing a metallurgical inspection technique with an optical microscope, after which the test result was compared with the evaluation result. This study shows how creep-fatigue crack initiation for a high-temperature structure can be predicted with conservatism per the RCC-MR A16 guide.

2005년 말을 기준으로 우리나라의 농림업 생산액은 총 36.3조원으로 이중 축산업 생산액은 11.8조원으로 전체 생산액의 32.5%를 차지하여 가장 많은 비율을 점유하고 있으며(농림부, 2006), 유제품의 소비량도 꾸준히 증가하여 1인당 63.6kg의 우유․유제품을 섭취하는 것으로 나타났다(농촌경제연구원, 2005). 이 같은 성장은 축산농가들이 국제 경쟁력 확보를 위해 그동안 보여준 각고의 노력과 꾸준한 투자의 결과로 평가되고 있으며, 이제는 축산물이 국민의 식생활에서 없어서는 안될 중요한 위치를 차지하게 되었다. 우리나라의 가축사육두수는 1970년대부터 해마다 계속 증가하여 2005년 말 현재 한우 1,819천두, 젖소 479천두, 돼지 8,962천두, 닭 109,628천수가 사육되고 있으며 사육농가의 전업화로 인하여 농가수는 점차 줄어들고 있는 반면에 농가당 사육두수는 증가하고 있는 실정이다(농림부, 2005). 농가당 평균 가축사육두수는 한우 8.8두, 젖소 51.7두, 돼지 671.4두, 닭 813.0수이며, 이중 부업이 아닌 전업농으로 볼 수 있는 한우 50두 이상의 사육농가가 전체 한우농가의 2.9%, 젖소 50두 이상 사육농가가 46.8%, 돼지 1,000두 이상의 농가가 21.6%, 닭 30,000수 이상의 농가가 1.0%를 차지하고 있어, 젖소가 다른 축종에 비해 전업농의 규모가 가장 많이 이루어졌다고 볼 수 있다(농림부, 2005). 따라서 매년 축산농가로부터 발생되는 분뇨의 양도 증가되고 있으며, 1990년초부터는 가축분뇨가 작물의 비료원으로 쓰이는 순기능보다는 환경오염의 한 요인으로 지목되면서 토양, 수질 및 대기오염이라는 역기능이 더 부각됨에 따라 도시근교의 낙농가, 초지나 사료작물포를 확보하지 못한 목장, 상수원 보호구역내에 위치한 목장에서는 분뇨처리에 고심을 하지 않을 수 없게 되었다. 특히 체격이 크고 방목지 및 운동장 등의 야외에서 사육되는 경우가 많은 젖소는 다른 가축에 비해 분뇨배설량이 많을 뿐 아니라, 운동장 등 축사 외부에서 활동하는 시간이 많기 때문에 주변으로부터 환경을 오염시키는 주범으로 지목을 받아 왔다. 또한 조사료 생산기반인 동시에 생산된 분뇨를 환원해야 할 경지면적이 협소한 상황에서 이루어진 젖소의 규모확대는 가축분뇨의 토양에 대한 부하를 높이게 되었고, 하천의 수질을 오염시키는 환경오염의 주범으로 인식되어 왔다. 이와같은 대내외적인 요인으로 인해 낙농가들은 목장의 규모에 관계없이, 분뇨를 적절하게 처리하는 것이 목장관리에 필수적인 사항으로 인식하게 되었다. 가축분뇨는 2, 3차 산업에서 발생하는 폐기물과는 그 성격 자체가 판이하게 달라 제도적 접근 방식도 나라와 환경에 따라 현격하게 다르다. 미국과 EC의 경우는 가축분뇨 자체를 환경보전재(Natural Resource)로 규정하고 적정한 사용방법을 정립하여 계도(Guide) 하므로서 환경을 보전하는 적극적인 환경보전 제도를 채택하고 있으며, 일본의 경우는 방류수의 수질을 규제하는 소극적 환경보전 제도로 출발했으나 1993년부터는 환경보전형 농업(축산)으로 정책방향을 전환하여 실행해 오고 있다. 우리나라도 이미 1981년부터 가축분뇨에 의한 환경오염 방지제도(법)가 시행되어 왔으나 법의 시행으로부터 25년이 경과한 현재까지도 가축분뇨에 의한 환경오염은 사회로부터 계속 지탄을 받고 있는 상태이다. 가축분뇨의 처리방식은 축종이나 농가 경영여건별로 크게 다르나, 궁극적으로는 경작지에 퇴비․액비 형태로 살포하여 이용

This study was conducted to determine fertilizer nutrient and pollutant production of Holstein dairy cattle by estimating manure characteristics. The moisture content of feces was 83.9% and 95.1% for urine. The pH of feces and urine were in the ranges of 7.0～7.4 and 7.5～7.8, respectively. The average BOD5, COD, SS, T-N, T-P concentrations of the dairy feces were 18,294, 52,765, 102,889, 2,575, and 457mg/ℓ, respectively. Dairy urine showed lower levels of BOD5(5,455mg/ℓ), COD(8,089mg/ℓ), SS(593mg/ℓ), T-N(3,401mg/l), and T-P(13mg/ℓ) than feces. The total daily produced pollutant amounts of a dairy cow were 924.1g(Milking cow), 538.8g(Dry cow), 284.4g(Heifer) of BOD5, 2,336.5g (Milking cow), 1,651.8g(Dry cow), 734.1g(Heifer) of COD and 4,210.1g(Milking cow), 2,417.1g(Dry cow), 1,629.1g(Heifer) of SS and 194.8g(Milking cow), 96.4g(Dry cow), 58.3g(Heifer) of T-N and 24.0g(Milking cow), 10.2g(Dry cow), 6.1g(Heifer) of T-P. The calculated amount of pollutants produced by a 450kg dairy cow for one year were 181.3kg of BOD5, 492.5kg of COD, 899.9kg of SS, 36.0kg of T-N and 4.1kg of T-P. The total yearly estimated pollutant production from all head(497,261) of dairy cattle in Korea is 90,149 tons of BOD5, 244,890 tons of COD, 447,491 tons of SS, 17,898 tons of T-N and 2,008 tons of T-P. The fertilizer nutrient concentrations of dairy feces was 0.26% N, 0.1% P2O5 and 0.14% K2O. Urine was found to contain 0.34% N, 0.003% of P2O5 and 0.31% K2O. The total daily fertilizer nutrients produced by dairy cattle were 197.4g (Milking cow), 97.4g(Dry cow), and 57.9g(Heifer) of Nitrogen, 54.2g(Milking cow), 22.2g(Dry cow), and 14.2g(Heifer) of P2O5 and 110.8g(Milking cow), 80.4g (Dry cow), and 39.5g(Heifer) of K2O. The total yearly estimated fertilizer nutrient produced by a 450kg dairy animal is 36.2kg of N, 8.8kg of P2O5, 24.6kg of K2O. The estimated yearly fertilizer nutrient production from all dairy cattle in Korea is 18,000 tons of N, 4,397 tons of P2O5, 12,206 tons of K2O. Dairy manure contains useful trace minerals for crops, such as CaO and MgO, which are contained in similar levels to commercial compost being sold in the domestic market. Concentrations of harmful trace minerals, such as As, Cd, Hg, Pb, Cr, Cu, Ni, Zn, met the Korea compost standard regulations, with some of these minerals being in undetected amounts.

In this study, a rocking behavior experiment using a guide plate and a guide channel to prevent lateral deformation of a steel damper was planned. For this purpose, strut I-type specimen I-1 and strut S-type specimen S-1 were prepared. The experimental results were compared with the existing experimental results of SI-260 and SS-260 under the same conditions without the details of lateral deformation prevention in order to evaluate the effect of preventing lateral deformation. The damper with lateral deformation prevention detail was evaluated to have superior strength capacity, deformation capacity, and energy dissipation capacity than the damper without it. Therefore, the lateral deformation prevention detail was evaluated to have a good effect in improving the design capability of the steel damper.

The UTM-01 developed in 1998 was the first maglev vehicle in Korea for the urban transit maglev (UTM) system. Through the improvement of UTM-01 and development of UTM02, the commercialization of the UTM system is being prepared now. In order to prepare for the commercialization of maglev, it is necessary that an optimal design of the levitation magnet should be provided for the safe operation of the vehicle. The levitation force is formed through the function of magnetic flux density on the top of magnet poles and gap between magnet pole and guide rail. To generate a magnetic field that is high enough to levitate the vehicle, ferromagnetic materials, such as pure iron for magnet pole and SS400 for guide rail, were used. The heat generated by $I^2R$ loss of magnet conductor makes the thermal convection on the surface of magnet including coil and poles. As these two characteristics are nonlinear phenomena, this paper deals with the nonlinear analysis on the magnetic and thermal properties of the U-type levitation magnet by using 3-D finite element method (FEM). Base on the analysis results, a small scale U-type magnet was designed, manufactured, and tested and it was verified that the magnet manufactured was satisfactory to all the design specifications.

Statement of problem: Shade selection has traditionally been accomplished by visual examination, which is particularly relevant to the shade selection of anterior teeth, but the subjective nature of visual analysis can lead to errors in shade matching. Recently shade selection systems have been developed to provide a more objective and scientific approach to understanding and clarifying shade selection. Purpose : The purpose of this study was analysis of various shade analyzing equipment with the goal of providing a more objective shade selection. Materials and method: Visual shade matching system selection(Vita Lumin Vacuum shade guide, Vitapan 3D Master shade guide) and mechanical shade matching method($ShadeEye^{(R)}$-EX Chroma Meter, $Shadescan^{TM}$ System) used for this study. The shade guide tap specimens for 10 extracted maxillary anterior teeth were produced by selecting shades using each shade matching system. The accuracy of the selection of shades for the teeth and fabricated specimens were evaluated by analyzing the calculated shade difference(${\Delta}E^*$), using a spectrophotometer and calculating the output of value $L^*,\;a^*,\;b^*$. Results and conclusion: The results show that the average ${\{Delta}E^*$ value (difference of shade) of the shade tap specimens to the actual specimen decreased in the following order: Vita Lumin Vacuum Shade Guide(VL), $ShadeEye^{(R)}$-EX Chroma Meter(SE) Vitapan 3D Master Shade guide(V3), and $Shadescan^{TM}$ System(55) : and that there are significant statistical differences between the VL and SS (p<0.05). In the analysis of the ${\Delta}E^*$ (difference of shade) value,40% of the VL group was found to be less than 3.3 (limit value of shade tap specimens clinically acceptable), 60% in the V3 group, 50% in the SE group, and 80% in the SS group.

목적: 황반원공 수술 후 가스 충전안에서 파장 가변 빛간섭단층촬영을 이용하여 수술 후 초기에 황반원공의 폐쇄 여부를 확인할 수있는지 알아보고자 하였다. 대상과 방법: 특발성 황반원공으로 유리체절제술, 내경계막제거술 및 가스충전술을 시행 받은 10안을 대상으로 수술 후 1일, 2일에파장 가변 빛간섭단층촬영을 시행하여 황반원공의 상태를 확인하였다. 수술 후 30일에도 파장 가변 빛간섭단층촬영을 시행하여 수술후 초기에 확인한 황반원공 상태의 변화 여부를 확인하였다. 결과: 10안 중 6안(60%)에서 술 후 1일 황반원공의 상태를 확인할 수 있었다. 황반원공의 상태를 확인한 6안 중 5안(83%)은 원공의폐쇄 소견을 보였으며, 수술 후 30일에 시행한 빛간섭단층촬영에서도 폐쇄된 상태를 보였다. 나머지 4안(40%)에서는 가스-망막 경계면만 나타나 폐쇄 여부를 확인할 수 없었으며, 수술 후 30일에 시행한 빛간섭단층촬영에서 4안 중 1안(25%)은 황반원공이 열려 있었다. 결론: 파장 가변 빛간섭단층촬영을 이용하여 가스 충전안에서 수술 후 초기 황반원공의 상태를 확인할 수 있었다. 파장 가변 빛간섭단층촬영을 이용하여 초기에 황반원공의 폐쇄를 확인함으로써 수술 후 엎드리는 자세를 지속하는 기간을 줄이는 데 도움이 될 수 있을것이다.

Purpose: To investigate the ability to determine the postoperative status of macular hole (MH) in gas-filled eyes using swept source optical coherence tomography (SS-OCT). Methods: Ten eyes of 10 patients who underwent vitrectomy, internal limiting membrane peeling and gas tamponade for idiopathic MH were included in this study. The macular area was examined using SS-OCT on postoperative days 1, 2 and 30. Results: MH status was assessed in 6 eyes (60%) on postoperative day 1 and MH closure was confirmed in 5 of the 6 eyes (83%). MH remained closed in all 5 eyes at 1 month after surgery. Only gas-retinal interface was obtained in 4 eyes (40%) and unclosed MH was found in 1 of the 4 eyes (25%) at 1 month after surgery. Conclusions: The MH status can be determined using SS-OCT in the early postoperative period even in gas-filled eyes. Confirming early MH closure with SS-OCT can serve as an important guide to significantly shorten the duration of prone positioning while maintaining high closure rates.

This paper is concerned with the kinematic analysis of several linkage drives for mechanical presses. Load and velocity characteristics of conventional presses are illustrated and a design of new drive for a mechanical press is represented. In this regard, a crank-slider mechanism with arc crank-pin guide is introduced and compared with other linkage drives. Kinematic performances are analyzed in respect of load capacity, slide velocity characteristics using a developed SS-Plot program. The new linkage drive turns out to be effective in terms of load and velocity characteristics, and productivity.

A 24-month Advanced Power Reactor 1400 (APR1400) core with a very-low-boron (VLB) concentration has been investigated for an inherently safe and high-performance PWR in this work. To develop a high-performance APR1400 which is able to do the passive frequency control operation, VLB feature is essential. In this paper, the centrally-shielded burnable absorber (CSBA) is utilized for an efficient VLB operation in the 24-month cycle APR1400 core. This innovative design of the VLB APR1400 core includes the optimization of burnable absorber and loading pattern as well as axial cutback for a 24-month cycle operation. In addition to CSBA, an Er-doped guide thimble is also introduced for partial management of the excess reactivity and local peaking factor. To improve the neutron economy of the core, two alternative radial reflectors are adopted in this study, which are SS-304 and ZrO₂. The core reactivity and power distributions for a 2-batch equilibrium cycle are analyzed and compared for each reflector design. Numerical results show that a VLB core can be successfully designed with 24-month cycle and the cycle length is improved significantly with the alternative reflectors. The neutronic analyses are performed using the Monte Carlo Serpent code and 3-D diffusion code COREDAX-2 with the ENDF/B-VII.1.

At the Korea Institute of Radiological and Medical Sciences, physical human phantoms were developed to evaluate various radiation protection quantities, based on the mesh-type reference computational phantoms of the International Commission on Radiological Protection. The physical human phantoms were fabricated such that a radiophotoluminescent glass dosimeter (RPLGD) with a Tin filter, namely GD-352M, could be inserted into them. A Tin filter is used to eliminate the overestimated signals in low-energy photons below 100 keV. The measurement uncertainty of the RPLGD reader system based on GD-352M should be analyzed for obtaining reliable protection quantities before using it for practical applications. Generally, the measurement uncertainty of RPLGD systems without Tin filters is analyzed for quality assurance of radiotherapy units using a high-energy photon beam. However, in this study, the measurement uncertainty of GD-352M was analyzed for evaluating the protection quantities. The measurement uncertainty factors in the RPLGD include the reference irradiation, regression curve, reproducibility, uniformity, energy dependence, and angular dependence, as described by the International Organization for Standardization (ISO). These factors were calculated using the Guide to the Expression of Uncertainty in Measurement method, applying ISO/ASTM standards 51261(2013), 51707(2015), and SS-ISO 22127(2019). The measurement uncertainties of the RPLGD reader system with a coverage factor of k = 2 were calculated to be 9.26% from 0.005 to 1 Gy and 8.16% from 1 to 10 Gy. A blind test was conducted to validate the RPLGD reader system, which demonstrated that the readout doses included blind doses of 0.1, 1, 2, and 5 Gy. Overall, the E_n values were considered satisfactory.