• 한국자동차공학회논문집
• /
• 제22권4호
• /
• pp.65-71
• /
• 2014

As an important component of a fuel cell, the bipolar plate comprises a large proportion in the fuel cell's volume, weight and price. The bipolar plate is the most widely used; however, graphite bipolar plate is large in volume, brittle and therefore easily broken during assembling. In addition, due to its poor machinability, production costs a lot, unless mass production. Compared with the graphite bipolar plate, the metal bipolar plate has good machinability, high electric conductivity and strong mechanical strength; however, it corrodes easily and has a high contact resistance, so in order to prevent corrosion and reduce the contact resistance, the basic metal needs to be processed by use of electro polishing and coating. The water which is produced by electrochemical reactions in the fuel cell must be discharged smoothly. In this study, in order to prevent corrosion the processes of electro polishing and CrN coating were used. According to the presence or absence of these processes, the contact angles can be measured and different metal bipolar plates can be made, these plates can be used for comparing and analyzing the performance of the fuel cell.

• 한국학교보건학회지
• /
• 제22권2호
• /
• pp.169-181
• /
• 2009

Purpose: Mood disorders such as depression and bipolar disorder are a major mental health problem in college students. We investigate the prevalence of depression and bipolar disorder and the relevance of risk factors for these mood disorders among one college freshmen. Methods: The subjects were 2,865 college students who entered one university located in Seoul and Ansung in 2009. We used BDI (Beck Depression Inventory) for depression assessment and K-MDQ (Mood Disorder Questionnaire) for bipolar disorder assessment. Demographic and socioeconomic factors were measured by questionnaire. Height, weight, blood pressure, total cholesterol, complete blood cell count, and liver function test data were obtained by physical examination for freshmen. Chi-square test and multiple logistic regression were performed to analyze the possible risk factors for depression and bipolar disorder. Results: With different BDI cutoff value, 16 and 21, the prevalence of depression was 8.7% (male: 7.6%, female: 10.1%) and 2.4% (male: 2.5%, female: 2.3%), separately. 'Low economic status', 'urban birth place', and 'low grade at entrance' were significantly associated with depression. Using the original cutoff criterion, defined as clustering of 7 or more symptoms that caused moderate or severe problems, the prevalence of bipolar disorder was 1.3% (male: 1.4%, female: 1.1%). The risk factor of bipolar disorder was academic fields (art fields). Conclusion: Depression and bipolar disorder are common disease in college freshmen. Therefore, Campus-based mental health service program is needed to help with prevention of and early intervention of these mood disorders.

• Journal of the Korean Academy of Child and Adolescent Psychiatry
• /
• 제18권1호
• /
• pp.66-71
• /
• 2007

There has been increasing recognition of pediatric bipolar disorder in the psychiatric field during the past 10 years. The clinical presentation of this disorder in preadolescent is greatly debated and few studies have been conducted in Korea. The authors report 3 cases of children with bipolar I disorder whose clinical symptoms were improved after pharmacotherapy. The authors also review current concepts, debates and treatment of pediatric bipolar disorder.

• 한국신재생에너지학회:학술대회논문집
• /
• 한국신재생에너지학회 2005년도 춘계학술대회
• /
• pp.248-251
• /
• 2005

Graphite reinforced conductive polymer composites for PEMFC bipolar plates were fabricated by the compression molding technique. Graphite powder was mixed with an phenol resin to impart electrical property in composites. In this study, conductive polymer composites with high filler $loadings(>60wt.\%)$ were manufactured to accomplish high electrical conductivity above 100S/cm. The level of compaction is important because graphite powder increase electrical conductivity of composites by direct physical contact between particles. The optimum molding pressure according to filler was proposed experimentally. Various tests(electrical conductivity, flexural strength, compressive strength, leach test, etc) were carried out to verify the performance of fabricated composites for PEMFC bipolar plates. Fabricated composites have good electrical conductivity and mechanical strength. The results of leach test and contact angle measurement showed similar characteristics compared with commercial bipolar plates.

• 한국신재생에너지학회:학술대회논문집
• /
• 한국신재생에너지학회 2008년도 춘계학술대회 논문집
• /
• pp.73-76
• /
• 2008

Bipolar Plates for PEMFC have been a key component of fuel cells with MEA, thus in this research they have been fabricated by a compression molding technique after mixing graphite powder with phenol resin. The results have shown the prominent properties compared with those by foreign advanced company with respect to the electrical conductivity and flexural strength. In addition, it has been carried out that the Voltage-Current characteristics comparison according to the unit cell experiments of bipolar plates. As a result, we have obtained good performances and we are going to research the molding feasibility of bipolar plate's flow channel.

• 한국신재생에너지학회:학술대회논문집
• /
• 한국신재생에너지학회 2009년도 춘계학술대회 논문집
• /
• pp.389-391
• /
• 2009

The performance loss as pressurized by inside components like GDL and bipolar plate happened when assembling the PEMFC stack with clamping force. Numerical analysis of Gasket was carried out to analyze distribution of clamping pressure about the inside components. In case of the gasket, Mooney-Rivlin model which is the Strain Energy Function was used for numerical analysis. This result made the stress distribution of bipolar plate to expect.

• 한국신재생에너지학회:학술대회논문집
• /
• 한국신재생에너지학회 2006년도 추계학술대회
• /
• pp.320-323
• /
• 2006

A numerical study is made of a manifold and bipolar plate in polymer electrolyte fuel cells, the aim of the present study is to describe the characteristics of flow pattern In manifold and bipolar plate. The present work shows that the flow pattern in the bipolar plate is affected by the penetration flow through GDL characterized by clamping pressure and GDL intrusion in to a channel area. Manifold geometry also affects the flow distribution. The recirculation flow by bent duct destroy even distribution In manifold, the present work shows that corner rounding can improve the manifold performance.

• Journal of the Korean Academy of Child and Adolescent Psychiatry
• /
• 제31권2호
• /
• pp.88-93
• /
• 2020

Objectives: Mood disorder is highly comorbid with attention deficit/hyperactivity disorder (ADHD), and comorbid ADHD symptoms are associated with suicide risk. The aim of this study was to examine the association between comorbid ADHD symptoms and the number of suicide attempts among patients with unipolar and bipolar depression. Methods: In this cross-sectional study, 100 patients with either unipolar or bipolar depression constituted the final sample. Pearson's correlation and multiple regression analyses were conducted to examine the association between comorbid ADHD symptoms and suicide risk. Results: Among patients with bipolar depression, the number of suicide attempts was significantly correlated with ADHD symptoms (r=0.324, p<0.01). ADHD symptoms significantly predicted the number of suicide attempts (β=0.249, p<0.05). Conclusion: Our findings underscore the importance of screening and assessing ADHD symptoms in male young adults with depressive disorders.

• 한국세라믹학회지
• /
• 제54권1호
• /
• pp.33-37
• /
• 2017

Single phase niobium nitride (NbN) coatings were deposited using asymmetric bipolar pulsed dc sputtering by varying pulse frequency and duty cycle of pulsed plasmas. Crystal structure, microstructure, morphology and mechanical properties were examined using XRD, FE-SEM, AFM and nanoindentation. Upon increasing pulse frequencies and decreasing duty cycles, the coating morphology was changed from a pyramidal-shaped columnar structure to a round-shaped dense structure with finer grains. Asymmetric bipolar pulsed dc sputtered NbN coatings deposited at pulse frequency of 25 kHz is characterized by higher hardness up to 17.4 GPa, elastic modulus up to 193.9 GPa, residual compressive stress and a smaller grain size down to 27.5 nm compared with dc sputtered NbN coatings at pulse frequency of 0 kHz. The results suggest that the asymmetric bipolar pulsed dc sputtering technique is very beneficial to reactive deposition of transition-metal nitrides such as NbN coatings.

• 한국지능시스템학회논문지
• /
• 제14권2호
• /
• pp.125-129
• /
• 2004

There are several kinds of fuzzy set extensions in the fuzzy set theory. Among them, this paper is concerned with interval-valued fuzzy sets, intuitionistic fuzzy sets, and bipolar-valued fuzzy sets. In interval-valued fuzzy sets, membership degrees are represented by an interval value that reflects the uncertainty in assigning membership degrees. In intuitionistic fuzzy sets, membership degrees are described with a pair of a membership degree and a nonmembership degree. In bipolar-valued fuzzy sets, membership degrees are specified by the satisfaction degrees to a constraint and its counter-constraint. This paper investigates the similarities and differences among these fuzzy set representations.