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Kim, Hakhyun,Hwang, Heewon,Baek, Seonhyeok,Kim, Dohyun Elsevier 2018 Sensors and actuators. A, Physical Vol.277 No.-
<P><B>Abstract</B></P> <P>We report <I>for the first time</I> an electrolytic micropump based on an electrode chip fabricated on a printed circuit board (PCB), and compare its performance with that of a micropump based on an electrode chip fabricated using conventional microfabrication. Gold interdigitated (IDT) electrodes are patterned on a PCB to minimize ohmic loss during electrolysis. Custom-built acrylic fixtures are used to characterize pumping performance of various electrode chips with different electrode shapes and materials. Hydrogen and oxygen gas bubbles produced by electrolysis generate liquid flow inside a microchannel. As predicted by the theory of water electrolysis, the micropump produces flow rate increasing linearly with current at a wide range (1 mA–2 A). Our micropump yields the maximum flow rate of 31.6 ml/min and maximum backpressure of 547 kPa (at 34 μl/min), significantly high compared with the previous micropumps based on various actuation mechanisms including piezoelectric actuation, electroosmosis and phase change. The PCB-based micropump with a thick electroplated-gold electrode (0.43 μm) chip shows the overall best performance in terms of flow generation, power consumption and cost, compared with the PCB-based pump using an thin electroless-gold electrode (0.04 μm) and the pump using a microfabricated chip with a sputtered gold electrode (0.2 μm). We anticipate the PCB-based electrolysis pump will be used in portable lab-on-a-chip devices where an integrated microscale pressure source with low power consumption and simple fabrication is crucial.</P> <P><B>Highlights</B></P> <P> <UL> <LI> An electrolytic micropump based on PCB technology for portable lab-on-a-chip devices is designed, fabricated and characterized. </LI> <LI> A theoretical model for pump power consumption as a function of electrode geometry is proposed and experimentally verified. </LI> <LI> Flow rate and backpressure of the micropump are measured as a function of current using custom-built jigs and experimental setups. </LI> <LI> Performance of our micropumps is thoroughly compared with that of the micropump made using conventional microfabrication. </LI> <LI> Our PCB micropump with electroplated gold electrode yields exceptionally high flow rate up to 31.6 ml/min and backpressure up to 547 kPa. </LI> </UL> </P>
Evaluation of Hypertriglyceridemia as a Mediator Between Endocrine Diseases and Pancreatitis in Dogs
Kim, Hakhyun,Kang, Ji-Houn,Heo, Tae-Young,Kang, Byeong-Teck,Kim, Gonhyung,Chang, Dongwoo,Na, Ki-Jeong,Yang, Mhan-Pyo American Animal Hospital Association 2019 The Journal of the American Animal Hospital Associ Vol.55 No.2
Serum 25-hydroxyvitamin D concentrations in dogs with suspected acute pancreatitis
KIM, Dong-In,KIM, Hakhyun,SON, Purum,KANG, Ji-Houn,KANG, Byeong-Teck,YANG, Mhan-Pyo The Japanese Society of Veterinary Science 2017 The Journal of veterinary medical science Vol.79 No.8
<P>The present study aimed to determine whether circulating serum concentrations of 25-hydroxyvitamin D [25-(OH) D] differed between healthy dogs and dogs with acute pancreatitis (AP). Twenty-two healthy dogs and twenty client-owned dogs with AP were enrolled in the study. Serum concentrations of 25-(OH) D, blood ionized calcium (iCa), and serum C-reactive protein (CRP) were measured. Concentrations of serum 25-(OH) D and blood iCa in dogs with AP were significantly lower than those of healthy dogs, and serum concentrations of CRP in dogs with AP were significantly higher than those of healthy dogs. A significant difference in 25-(OH) D serum concentrations was observed between survivor and non-survivor dogs with AP. After resolution of clinical signs, concentrations of serum 25-(OH) D, blood iCa, and serum CRP did not differ compared to those before treatment. This study shows that dogs with AP exhibit decreased 25-(OH) D levels, which might be associated with calcium imbalances and mortality rate in canine AP.</P>
Kim, Hakhyun,Kang, Ji-Houn,Chang, Dongwoo The Korean Society of Veterinary Science 2018 大韓獸醫學會誌 Vol.58 No.2
A 13-year-old spayed female Miniature Schnauzer was presented with complaints of intermittent syncope. Pericardial effusion was confirmed based on the physical examination, thoracic radiographs and echocardiography. Subsequently, prompt pericardiocentesis was performed. Clinical abnormalities were immediately improved after pericardiocentesis. However, the clinical signs associated with acute collapse recurred. After the second pericardiocentesis, thoracic radiographs revealed pleural effusion, and the clinical signs resolved rapidly. The dog underwent pleural aspiration. Analysis of pleural fluid revealed almost similar features as the previous pericardial fluid. It was possible that a pericardial-pleural fistula was created during the pericardiocentesis. The pericardial and pleural effusion disappeared after the procedures.
김학현 ( Hakhyun Kim ),유환규 ( Hwankyu Yoo ),오하영 ( Hayoung Oh ) 한국정보처리학회 2023 정보처리학회논문지. 소프트웨어 및 데이터 공학 Vol.12 No.2
Since the COVID-19 era, the rise in apartment prices has been unconventional. In this uncertain real estate market, price prediction research is very important. In this paper, a model is created to predict the actual transaction price of future apartments after building a vast data set of 870,000 from 2015 to 2020 through data collection and crawling on various real estate sites and collecting as many variables as possible. This study first solved the multicollinearity problem by removing and combining variables. After that, a total of five variable selection algorithms were used to extract meaningful independent variables, such as Forward Selection, Backward Elimination, Stepwise Selection, L1 Regulation, and Principal Component Analysis(PCA). In addition, a total of four machine learning and deep learning algorithms were used for deep neural network(DNN), XGBoost, CatBoost, and Linear Regression to learn the model after hyperparameter optimization and compare predictive power between models. In the additional experiment, the experiment was conducted while changing the number of nodes and layers of the DNN to find the most appropriate number of nodes and layers. In conclusion, as a model with the best performance, the actual transaction price of apartments in 2021 was predicted and compared with the actual data in 2021. Through this, I am confident that machine learning and deep learning will help investors make the right decisions when purchasing homes in various economic situations.