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Heo, Kookjin,Lee, Jeong-Seon,Kim, Ho-Sung,Kim, Min-Young,Jeong, Hyejeong,Kim, Jaekook,Lim, Jinsub The Electrochemical Society 2018 Journal of the Electrochemical Society Vol.165 No.13
<P>The advantage of the co-precipitation method is that the precursors react uniformly at the molecular level. Both Ni-rich cathode materials and garnet-type lithium-ion conductor materials have typically been synthesized by the co-precipitation method. In this paper, we report on a composite of lithium-ion conductive and Ni-rich cathode materials with improved electrochemical properties, synthesized by simultaneous co-precipitation. This process is a very simple and useful method for preparing the composite due to uniform precipitation from the precursor phase. The physical, chemical, and electrochemical characteristics of the ionic conductor Ni-rich cathode composite material were investigated. (C) 2018 The Electrochemical Society.</P>
Jeong HyeJeong,정성원,Heo Tae Gil,Choi Pyong Wha,Kim Jae Il,Jung Sung Min,Jun Heungman,신용찬,Um Eunhae 대한외상학회 2022 大韓外傷學會誌 Vol.35 No.3
Purpose: The purpose of this study was to determine whether a higher Injury Severity Score (ISS) could serve as an indicator of splenectomy in patients with traumatic splenic lacerations. Methods: A total of 256 cases of splenic laceration were collected from January 1, 2005 to December 31, 2018. After the application of exclusion criteria, 105 were eligible for this study. Charts were reviewed for demographic characteristics, initial vital signs upon presentation to the emergency room, Glasgow Coma Scale, computed tomography findings, ISS, and treatment strategies. The cases were then divided into nonsplenectomy and splenectomy groups for analysis.Results: When analyzed with the chi-square test and t-test, splenectomy was associated with a systolic blood pressure lower than 90 mmHg, a Glasgow Coma Scale score lower than 13, active bleeding found on computed tomography, a splenic laceration grade greater than or equal to 4, and an ISS greater than 15 at presentation. However, in multivariate logistic regression analysis, only active bleeding on computed tomography showed a statistically significant relationship (P=0.014).Conclusions: Although ISS failed to show a statistically significant independent relationship with splenectomy, it may still play a supplementary role in traumatic splenic injury management.
Im, Jehong,Heo, Kookjin,Kang, Sung-Won,Jeong, Hyejeong,Kim, Jaekook,Lim, Jinsub Electrochemical Society 2019 Journal of the Electrochemical Society Vol.166 No.15
<P>Increased demand for lithium resources has led to increased Li costs and supply problems and increased the importance of lithium ion battery (LIB) recycling. In this study, lithium phosphate from LIB recycling wastewater was refined in a simple process using deionized water (DI). The morphologies and compositions associated with purifying Li<SUB>3</SUB>PO<SUB>4</SUB> were investigated using X-ray diffraction, field emission-scanning electron microscopy, simultaneous thermogravimetric-differential thermal analysis, differential scanning calorimetry, pH measurement, inductively coupled plasma optical emission spectroscopy, and carbon and sulfur determinators. Simple refining with DI can increase Li<SUB>3</SUB>PO<SUB>4</SUB> purity from 94.601% to 98.867%. LiFePO<SUB>4</SUB> (LFP) was then synthesized using the purified Li<SUB>3</SUB>PO<SUB>4</SUB>; its morphology was studied and its electrochemical performance evaluated by constant current charge/discharge testing and cyclic voltammetry. The LFP cathode fabricated from purified Li<SUB>3</SUB>PO<SUB>4</SUB> exhibited improved electrochemical properties, particularly in terms of initial capacity and cycling stability.</P>
Degradation of All-Solid-State Lithium-Sulfur Batteries with PEO-Based Composite Electrolyte
Lee, Jongkwan,Heo, Kookjin,Song, Young-Woong,Hwang, Dahee,Kim, Min-Young,Jeong, Hyejeong,Shin, Dong-Chan,Lim, Jinsub The Korean Electrochemical Society 2022 Journal of electrochemical science and technology Vol.13 No.2
Lithium-sulfur batteries (LSBs) have emerged as a promising alternative to lithium-ion batteries (LIBs) owing to their high energy density and economic viability. In addition, all-solid-state LSBs, which use solid-state electrolytes, have been proposed to overcome the polysulfide shuttle effect while improving safety. However, the high interfacial resistance and poor ionic conductivity exhibited by the electrode and solid-state electrolytes, respectively, are significant challenges in the development of these LSBs. Herein, we apply a poly (ethylene oxide) (PEO)-based composite solid-state electrolyte with oxide Li<sub>7</sub>La<sub>3</sub>Zr<sub>2</sub>O<sub>12</sub> (LLZO) solid-state electrolyte in an all-solid-state LSB to overcome these challenges. We use an electrochemical method to evaluate the degradation of the all-solid-state LSB in accordance with the carbon content and loading weight within the cathode. The all-solid-state LSB, with sulfur-carbon content in a ratio of 3:3, exhibited a high initial discharge capacity (1386 mAh g<sup>-1</sup>), poor C-rate performance, and capacity retention of less than 50%. The all-solid-state LSB with a high loading weight exhibited a poor overall electrochemical performance. The factors influencing the electrochemical performance degradation were revealed through systematic analysis.
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김현주(Hyun Joo Kim),윤혜정(Hyejeong Yun),이준헌(Jun Heon Lee),허강녕(Kang Nyeong Heo),강보석(Bo Seok Kang),조철훈(Cheorun Jo) 충남대학교 농업과학연구소 2012 농업과학연구 Vol.39 No.2
This study was examined the optimization of processing conditions for taste-assurance factors of boiled Korean native chicken (KNC) through response surface methodology. The effects of two independent variables, including heating time (X1) and water volume (X2), were investigated using central composite design. Hypoxanthine content, lipid oxidation, texture, and sensory results were chosen as dependent variable. Results showed high reliability on hypoxanthine and texture property in leg meat (not breast meat) of boiled KNC. Statistical modeling revealed that 3.5 folds of added water (v/w) based on chicken weight and 73.5 min of cooking time was the optimum for producing characteristic taste and textural properties from the leg meat of KNC.
Improving Culture Performance and Antibody Titer in CHO Cell Fed-batch Culture by Controlling pH
Sang Yeop LEE,Seungjib JEON,Mi Rae KIM,Hyejeong HEO,Byung Cheon LEE,Joon-Chul LEE 한국생물공학회 2021 한국생물공학회 학술대회 Vol.2021 No.10
Mammalian cell culture is most common industrial process for the production of recombinant proteins. However, higher cell density and titer are still limited due to factors such as excessive metabolites production, nutrients limitation, and high osmolality. Lactate is the major product from glucose metabolism, and lactate accumulation has been demonstrated to inhibit growth rate and negatively affect antibody production in mammalian cells. To partly overcome this factor, we investigated a simple method using pH control in Chinese hamster ovary (CHO) cells. We performed CHO-DG44 fed-batch cultures under pH conditions (6.9 and 7.0) using rocking bioreactor. As a result, cells grown under low pH condition produced lactate approximately 70% lower than cells grown under high pH condition. We also found that peak viable cell density (PVCD) and final antibody titer were increased in fed-batch culture under low pH condition. Taken together, our results demonstrate that fed-batch culture under pH of 6.9 improves the PVCD and titer in CHO cell culture.Mammalian cell culture is most common industrial process for the production of recombinant proteins. However, higher cell density and titer are still limited due to factors such as excessive metabolites production, nutrients limitation, and high osmolality. Lactate is the major product from glucose metabolism, and lactate accumulation has been demonstrated to inhibit growth rate and negatively affect antibody production in mammalian cells. To partly overcome this factor, we investigated a simple method using pH control in Chinese hamster ovary (CHO) cells. We performed CHO-DG44 fed-batch cultures under pH conditions (6.9 and 7.0) using rocking bioreactor. As a result, cells grown under low pH condition produced lactate approximately 70% lower than cells grown under high pH condition. We also found that peak viable cell density (PVCD) and final antibody titer were increased in fed-batch culture under low pH condition. Taken together, our results demonstrate that fed-batch culture under pH of 6.9 improves the PVCD and titer in CHO cell culture.
Seungjib JEON,Hyun Gi KOH,Mi Rae KIM,Young Jin KIM,Hyejeong HEO,Joon-Chul LEE,Yong Keun CHANG 한국생물공학회 2021 한국생물공학회 학술대회 Vol.2021 No.10
Microalgae are promising resources for producing value-added products due to their rapid growth rate and high lipid content. Among products obtained from microalgae, the eicosapentaenoic acid (EPA) which is health supplement has gained attention because of the limitations on fish oil production. In this study, we optimized cultivation conditions of Nannochloropsis salina for enhancement of EPA production. The optimization process was carried out by response surface methodology (RSM) for studying the interactive effect of temperature and N concentration (NaNO₃) using central composite design. The RSM results showed an optimal level of 1.28 g/L for NaNO₃ and 21 ℃ for temperature, resulting in maximum EPA productivity of 14.4 ㎎/L/day. To understand the effect of optimal conditions on EPA production, we analyzed the lipid compositions and pigment contents. The glycolipids and chlorophyll a were found to be increased under optimal conditions. We also investigated mRNA expression levels of genes involved in EPA synthesis by quantitative real-time PCR and confirmed their positive contribution to EPA production.