The present research focuses on the tribological behavior of the AA5083 alloy-based hybrid surface composite using aluminosilicate and multi-walled-carbon nanotube through friction stir processing for automotive applications. The friction stir processing parameters (tool rotation and traverse speed) are varied based on full factorial design to understand their influence on the tribological characteristics of the developed hybrid composite. The surface morphology and composition of the worn hybrid composite are examined using a field-emission scanning electron microscope and an energy-dispersive x-ray spectroscope. No synergistic interaction is observed between the wear rate and friction coefficient of the hybrid composite plate. Also, adhesive wear is the major wear mechanism in both base material and hybrid composite. The influence of friction stir process parameters on wear rate and the friction coefficient is analyzed using the hybrid polynomial and multi-quadratic radial basis function. The models are utilized to optimize the friction stir processing parameters for reducing the rate of wear and friction coefficient using multi-quadratic RBF algorithm optimization.

In this study, we proposed a simulator for the development of a digital multi-process welding machine and a welding process monitoring system. The simulator, which mimics the data generation process of the welding machine, is composed of process control circuit, peripheral device circuit, and wireless communication circuit. Utilizing this simulator, we aimed to develop a welding process monitoring system that can monitor the welding situations of four multi-process welding machines and three processes each, with data transmission through wireless communication. Through the operation of the proposed simulator, sequential digital processing of multi-process welding data and wireless communication were achieved. The welding process monitoring system enabled real-time monitoring and accumulation of the process data. The selection of upper and lower limits for process variables was carried out using a deep neural network based on allowable changes in bead shape, enabling the management of welding quality by applying a process control technique based on the trend of received data.

From Fukushima nuclear disaster, as the water which is supplied by rain and groundwater flow into reactor building, contaminated water which contains radioactive nuclides is occurred. Although about 600 tons of contaminated water was generated at the early of accident, as the groundwater management system is developing, about 150 tons of contaminated water is generated now. Tokyo Electric Power Holdings (TEPCO) operate a multi-nuclide removal equipment which is called ‘ALPS’ and store purified water (ALPS treated water) in the Fukushima NPP site by tank. From 2023, the Japanese government decided to dilute the stored ALPS treated water and discharge it into the ocean to secure space on the site. In this study, based on the data opened to the public by TEPCO, the current status of ALPS is investigated. The dilution and discharge process under conceptual design was investigated. In addition, the treatment capacity of ALPS was analyzed based on the radioactivity concentration data of 7 nuclides. And then, two points to be checked found. First, it was confirmed that the performance of ALPS temporarily decreased between 2015 and 2018 due to reduced replacement cycle of filter and absorbent. Second, it was confirmed that the ALPS treated water from specific ALPS still haven’t satisfied the discharge limit for I-129, Sr-90, and Cs-137. In the case of Cs-137, about 1.7 times the radioactivity concentration was detected compared to the discharge limit. For I-129 and Sr-90, about 2.4 times and 2.1 times of radioactivity concentration was detected compared to the discharge limit. From this study, some of the ALPS treated water are confirmed that the radioactivity concentration exceeds the discharge limit, and the treatment capacity of ALPS might be unstable depend on the ALPS operation such as replacement cycle. Therefore, before the discharging of contaminated water on 2023, it is necessary to inspect ALPS if it purifies contaminated water with reliability or not, and to secure the reliable evaluation method to measure radioactivity concentration.

Most of automobile steering parts are manufactured through the multi-stage cold forging process using round-bar drawn materials. The same process is applied to the ball stud parts of the outer ball joint, and various research activities are being carried out to reduce the extreme manufacturing cost in order to survive in the limitless competition. In this paper, we present a quantitative prediction method for the limiting life of the die as a method for cost reduction in the multi-stage cold forging process. The load on the die was minimized by distributing the forming load based on process optimization through finite element analysis. In addition, based on the quantitative prediction algorithm of the limiting life of the die, the application of the split die and the optimization of the phosphate treatment of the material surface are presented as a conclusion as a method to improve the limiting life of the die.

Tributyl phosphate (TBP) is a well-known and important compound in the nuclear industry for the nuclear fuel reprocessing, and it is also used in a various field such as plastic industry as antifoaming agent. Untreated organic pollutants in TBP can remain in the soil water and cause serious environmental pollution, thus it should be degraded through environmentally friendly methods. The non-thermal plasma-based advanced oxidation process (AOP) is one of the most widely studied and best developed processes owing to its simple structure and ease of operation. In this study, a plasma-based AOP was stably generated using submerged multi-hole dielectric barrier discharge (DBD) and applied to relatively high concentration of TBP solution. A submerged DBD plasma system was designed to directly interact with water, thereby producing reactive oxygen species (ROS) and functioning as a powerful oxidizer. Additionally, UV, O3, and H2O2 are generated by the developed plasma system without using any other additives to produce OH radicals for degrading organic pollutants; therefore, this system circumvents the use of complex and advanced oxidation processes. The electrical properties and concentrations of the active species were analyzed to establish optimal plasma operating conditions for degrading TBP solution. The results were analyzed by measuring the total organic carbon (TOC) and changes in solution properties. Based on these results, a degradation mechanism of TBP solution is proposed. After 50 min of plasma treatment, the concentration of TOC was gradually decreased. Consequently, we found that plasma-based AOP using submerged multi-hole DBD has advantages as an alternative technology for degrading organic pollutants such as TBP solution.

In this study, as part of the paradigm shift for manufacturing innovation, data from the multi-stage cold forging process was collected and based on this, a big data analysis technique was introduced to examine the possibility of quality prediction. In order for the analysis algorithm to be applied, the data collection infrastructure corresponding to the independent variable affecting the quality was built first. Similarly, an infrastructure for collecting data corresponding to the dependent variable was also built. In addition, a data set was created in the form of an independent variable-dependent variable, and the prediction accuracy of the quality prediction model according to the traditional statistical analysis and the tree-based regression model corresponding to the big data analysis technique was compared and analyzed. Lastly, the necessity of changing the manufacturing environment for the use of big data analysis in the manufacturing process was added.

Forged part made of Cold heading quality wire materials are used for automotive brake systems. The cost reduction of forged products is a major issue because of the strict shape change. A series of studies were conducted to minimize the cost of EPB spindle process among brake parts. In order to reduce the material cost, heat treatment-abbreviated material was applied and the formability on the processes was verified by the ductile fracture theory. In addition, the causes of shape fixation and die life degradation were analyzed using the numerical simulation. The process cost has been minimized by re-designing process, changing the product shape, and the die material.

In this study, using a wet chemical process, we evaluate the effectiveness of different solution concentrations in removing layers from a solar cell, which is necessary for recovery of high-purity silicon . A 4-step wet etching process is applied to a 6-inch back surface field(BSF) solar cell. The metal electrode is removed in the first and second steps of the process, and the anti-reflection coating(ARC) is removed in the third step. In the fourth step, high purity silicon is recovered by simultaneously removing the emitter and the BSF layer from the solar cell. It is confirmed by inductively coupled plasma mass spectroscopy(ICP-MS) and secondary ion mass spectroscopy(SIMS) analyses that the effectiveness of layer removal increases with increasing chemical concentrations. The purity of silicon recovered through the process, using the optimal concentration for each process, is analyzed using inductively coupled plasma atomic emission spectroscopy(ICP-AES). In addition, the silicon wafer is recovered through optimum etching conditions for silicon recovery, and the solar cell is remanufactured using this recovered silicon wafer. The efficiency of the remanufactured solar cell is very similar to that of a commercial wafer-based solar cell, and sufficient for use in the PV industry.

This study is about the process capability index (PCI). In this study, we introduce several indices including the index CPR and present the characteristics of the CPR as well as its validity. The difference between the other indices and the CPR is the way we use to estimate the standard deviation. Calculating the index, most indices use sample standard deviation while the index CPR uses range R. The sample standard deviation is generally a better estimator than the range R . But in the case of the panel process, the CPR has more consistency than the other indices at the point of non-conforming ratio which is an important term in quality control. The reason why the CPR using the range has better consistency is explained by introducing the concept of ‘flatness ratio’. At least one million cells are present in one panel, so we can’t inspect all of them. In estimating the PCI, it is necessary to consider the inspection cost together with the consistency. Even though we want smaller sample size at the point of inspection cost, the small sample size makes the PCI unreliable. There is ‘trade off’ between the inspection cost and the accuracy of the PCI. Therefore, we should obtain as large a sample size as possible under the allowed inspection cost. In order for CPR to be used throughout the industry, it is necessary to analyze the characteristics of the CPR . Because the CPR is a kind of index including subgroup concept, the analysis should be done at the point of sample size of the subgroup. We present numerical analysis results of CPR by the data from the random number generating method. In this study, we also show the difference between the CPR using the range and the CP which is a representative index using the sample standard deviation. Regression analysis was used for the numerical analysis of the sample data. In addition, residual analysis and equal variance analysis was also conducted.

In this study, a method to remove residual powder on a multi-layered graphene and a new approach to transfer multi-layered graphene at once are studied. A graphene one-step transfer (GOST) method is conducted to minimize the residual powder comparison with a layer-by-layer transfer. Furthermore, a residual powder removing process is investigated to remove residual powder at the top of a multi-layered graphene. After residual powder is removed, the sheet resistance of graphene is decreased from 393 to 340 Ohm/sq in a four-layered graphene. In addition, transmittance slightly increases after residual powder is removed from the top of the multi-layered graphene. Optical and atomic-force microscopy images are used to analyze the graphene surface, and the Ra value is reduced from 5.2 to 3.7 nm following residual powder removal. Therefore, GOST and residual powder removal resolve the limited application of graphene electrodes due to residual powder.

1970년대 중반 석유 파동 이후 대체 에너지 개발에 대한 관심이 커지면서 그 중에서 혐기성 공정에서 발생하는 바이오가스 생산과 활용 기술 개발에 대한 연구가 진행되고 있다. 바이오 가스의 주성분은 50-70%CH4/30-40%CO2으로 이루어져 있고 이 때 메탄을 > 95% 순도로 농축하면 도시가스와 자동차 연료로 사용이 가능하다. 바이오가스의 정제기술로 막 분리법은 낮은 에너지 소모량, 이동성 및 쉬운 작동성 등의 장점을 가지고 있다. 본 연구에서는 바이오가스를 95% 이상의 메탄으로 농축하기 위해 폴리설폰 중공사막과 다단 분리막 공정을 이용하였다. 분리막 공정에서 압력, 온도, 막면적 등 다양한 공정 변수에서 95% 이상의 메탄 순도를 얻기 위한 연구를 진행하였다.

본 연구에서는 막 결합형 축전식 탈염공정의 단수를 10단 형태의 모듈로 설계하여 처리용량을 증대하고자 하였다. MCDI에 사용된 이온교환고분자로는 아민기가 함유된 폴리설폰(APSf)과 술폰기가 함유된 폴리이서이서케톤(SPEEK)을 합성하여 캐스팅법으로 탄소전극에 제조하였다. 공정변수는 흡착전압 및 시간, 탈착전압 및 시간, 공급액의 유속과 농도 등을 달리하여 염 제거효율을 측정하였다. 대표적으로 Nacl 100 mg/L, 유속 100 mL/min, 흡착조건 1.2 V/3 min, 탈착조건 -0.5 V/5 min에서 98.3%의 염 제거효율을 보였다.

바이오가스를 98% 이상의 고순도 메탄가스로 정제하여 자동차연료나 도시가스로 활용한다면 경제적으로 매우 큰 효과를 기대할 수 있다. 본 연구에서는 음 식물쓰레기 처리시설에서 발생하는 바이오가스를 정제하여 98% 이상의 고순도 메탄가스를 95% 이상 분리 회수하는 분리막 정제 시스템 개발을 하고자 하였다. 분리막 공정 설계에 필요한 데이터를 확보하기 위하여 분리막 모듈의 이산화탄소/메탄 혼합기체 분리시험을 수행하였으며, 다양한 운전조건에서 얻어진 실험결과를 바탕으로 공정설계를 수행하였다. 최종 생산되는 메탄 순도 98%, 이산화탄소 순도 95% 이상을 만족하는 운전 조건에서 메탄, 이산화탄소 회수율과 이에 필요한 각 단의 막면적과 비율을 확인하였다.

본 연구에서는 막 결합형 축전식 탈염공정의 단위셀의 단수를 늘려 적층된 10단 형태의 모듈을 설계하여 제작하 였다. 아민기가 함유된 폴리설폰(APSf)과 술폰기가 함유된 폴리이서이서케톤(SPEEK)을 합성하였으며 캐스팅법으로 다공성 탄소전극에 코팅하여 제조하였다. 10단 모듈에 대하여 흡착전압 및 시간, 탈착전압 및 시간, 공급액의 유속과 농도 등의 운전 조건과 CaSO4, MgCl2 등의 2가 이온 용액과 수도수에 대하여 염 제거효율을 측정하였다. 대표적으로 NaCl 100 mg/L의 공급 액을 사용하였을 때, 유속 100 mL/min, 흡착조건 1.2 V/3 min, 탈착조건 -0.5 V/5 min에서 98.3%의 염 제거효율을 보였다.