A Comparison of Long-term Forecasting Methods: A Comment

Gawon Yoon(윤가원) 통계청 통계개발원 1998 통계연구 Vol.3 No.2

Should We Forecast Economic Time Series in Levels or in Logs?

Yoon, Gawon 釜山 大學校 經營 經濟 硏究所 2000 經營 經濟 硏究 Vol.19 No.1

경제 변수들은 일반적으로 로그 변환된 형태로 분석된다. 본고에서는, 공적분된 벡타 자귀회귀 모형을 사용하여, 로그 변환된 미국 GNP 및 투자자료가 그들의 수준변수보다 변수들의 수준을 보다 뛰어나게 예측한다는 것을 보였다. 이 결과가 다른 자료에 확장되어 일반적으로 적용될 수 있는지는 알려져 있지 않지만, 적어도 본고에서 사용한 자료의 경우에는 개선된, 변수의 수준 예측을 경제 변수를 로그 변환하는 이유의 하나로서 들 수 있다.

Forecasting Cointegrating relationships : an application to the spread between the US commercial paper and T-bill rates

Yoon, Gawon 釜山 大學校 經營 經濟 硏究所 1999 經營 經濟 硏究 Vol.18 No.1

Incorporating cointegrating relationships helps forecast cointegrated nonstationary variables. Little has been known, however, for the forecasting of the cointegrating relationship themselves, even though they are sometimes an interesting object of research; it is not clear whether better forecasts of cointegrating relationships are possible if cointegration is taken into consideration. In this paper, we forecast the spread between the six month US commercial paper and T-bill rates. While the two interest are nonstationary, their spread is stationary and is known to have some forecasting power for the future movements of economic activities. Four different information sets are considered in predicting the spread: A univariate information set of the present and past values of the spread, one with present and past values of the two interest rates composing a VAR process, the same bivariate system of interest rates with error correction model [ECMs]. and finally an ARX type model with common stochastic trends derived from ECMs as exogenous variables. It turns out that forecasts from VAR processes have the lowest root mean squared errors and dominate those from the ECMs and ARX type models. Therefore, the consideration of cointegrating relationship between the interest rates does not lead to improved forecasts of their spread. However, all the structural models are beaten by a naive forecast of no change, even though the spread is stationary. A shorter subsample period is also considered to test the robustness of the results. A possible explanation of the findings is provided.

Geometric ergodicity and regular variation of stochastic unit root processes

Gawon Yoon 한국계량경제학회 2007 한국계량경제학회 학술대회 논문집 Vol.2007 No.2

This paper shows that stochastic unit root [STUR] processes, which are closely related to standard (fixed) unit root models and could be easily confused with them by standard unit root tests, are geometrically ergodic and regularly varying. On the contrary to the widely held belief, therefore, STUR processes are not long-memory, but short-memory. The phenomena of volatility-induced stationarity and long-memory are also discussed under STUR.

선거와 시장경제Ⅱ-2000 국회의원 선거시장을 중심으로-

한경동(Kyungdong Hahn),신혁승(Hyukseung Shin),윤가원(Gawon Yoon) 한국경제연구원 2001 한국경제연구원 연구보고서 Vol.2001 No.-

This study is composed of three papers, which are related with the Political Stock Market to track the dynamics of election campaign, and to predict outcomes. One is a comprehensive and comparative review of the markets held in U.S.A., Canada, Australia, Sweden, Netherlands, Germany and Korea to find out factors to influence the function of the markets. The other one focuses on the 2000 Korean National Assembly Stock Market, secondly implemented in Korea by Assembly Stock Market, secondly implemented in Korea by Korea Economic Research Institute and Joongang Daily Newspaper after the 1998 Korean Presidential Market (KPSM). The predictions of the 2000 Korean National Assembly Stock Market was quite accurate to the outcome of the election. The forecasting errors were only 0.55~5.15% points to the Parties' actual vote shares. The third paper econometrically investigates the power of an unconventional Granger-causality test between opinion polls and political stock market prices implemented in Forsythe et al. (1992), through Monte Carlo simulations.

The relative importance of monetary and nonmonetary factors in the U.S. Economic recovery from 1933 to 1945 : 미국의 대공황 회복고정에서의 통화적 및 비통화적 요인의 상대적 중요성

Shin, Hyukseung 釜山大學校 商科大學 2000 釜山商大論集 Vol.71 No.-

Lyotropic liquid crystalline nanoparticles for oral delivery: formulation and evaluation of sustained-released cromolyn sodium loaded cubosomes

Dinh Linh,Kim Dong Min,Lee Gawon,Yoon Yangno,Han Hyeji,Oh Dong Joon,Lee Juseung,Hwang Sung-Joo 한국약제학회 2024 Journal of Pharmaceutical Investigation Vol.54 No.4

Purpose Cromolyn sodium, a so-called “mast cell stabilizer”, is well-known to prevent mast cells from triggering the immune response. However, the presence of twin carboxyl groups renders cromolyn sodium highly hydrophilic, hindering its entry into systemic circulation upon oral administration, consequently, hampering its absorption across the gastrointestinal tract and resulting in very poor bioavailability. The cubic phase of lyotropic liquid crystal systems is characterized by a unique structure with internal water channels surrounded by lipid bilayer membranes. In the current study, we prepared cromolynloaded monoolein cubosomes with different stabilizer concentrations and investigated the ability of cubosomes to deliver and improve cromolyn sodium oral availability. Methods Several formulations of liquid crystalline nanoparticles were prepared, and different stabilizer concentrations were tested to create a cubic phase dispersion. In vitro characterization, including morphological examination, particle size and polydispersity analysis, zeta potential analysis, entrapment efficiency of cubosomes, and drug release tests from cubosomes, were performed. Ex vivo intestinal permeation study, in vivo pharmacokinetic study, and cytotoxicity studies were also performed. Results Our results revealed that cromolyn sodium-loaded cubosomes could significantly sustain the drug release, with the formulations exhibiting the optimum particle size (about 100 nm), zeta potential (approximately –30mV), and polydispersity index (between 0.1 and 0.3) with entrapment efficiency of > 50%. The cubic shape was confirmed using transmission electron microscopy. The effects of the water and oil phase balance on the phase transition and drug load were addressed. The apparent permeability coefficients of the cubosomes were determined at predetermined time points. In the first 2 h, all cubosomal formulations exhibited higher permeability than that of cromolyn sodium, highlighting the capacity of cubosomes to facilitate drug diffusion across the intestinal membrane. The bioavailability of cromolyn sodium-loaded cubosomes with vitamin E and poloxamer 407 as surfactants was 1.3-fold higher than that of cromolyn sodium solution, achieving sustained release (Tmax = 8 h, Cmax = 63.23 μg/mL). Conclusion: Cubosomes, a lyotropic liquid crystal system, are promising carriers of cromolyn sodium and other hydrophilic drug molecules.

Folate-modified PLGA nanoparticles for tumor-targeted delivery of pheophorbide a <i>in vivo</i>

Son, Jihwan,Yang, Seung Mok,Yi, Gawon,Roh, Yoon Jin,Park, Hyeji,Park, Jae Myung,Choi, Myung-Gyu,Koo, Heebeom Elsevier 2018 Biochemical and biophysical research communication Vol.498 No.3

<P><B>Abstract</B></P> <P>Targeted drug delivery has been an important issue for tumor therapy including photodynamic therapy (PDT). The purpose of our study is to increase the targeting efficiency of photosensitizer (PS) using folate-modified nanoparticles (NPs) to tumor site <I>in vivo</I>. Folate receptor is over-expressed on the surface of many human cancer cells. We prepared poly (lactic-co-glycolic acid) (PLGA) NPs containing pheophorbide a (Pba), a PS that is used in PDT and generates free radical for killing cancer cells. The surface of NPs was composed of phospholipids modified with polyethylene glycol (PEG) and folate (FA). The size of the resulting FA-PLGA-Pba NPs was about 200 nm in PBS at pH 7.4 and they were stable for long time. They showed faster cellular uptake to MKN28 human gastric cancer cell line than control PLGA-Pba NPs by high-affinity binding with folate receptors on cell surface. In MTT assay, FA-PLGA-Pba NPs also showed enhanced tumor cell killing compared to control PLGA-Pba NPs. <I>In vivo</I> and <I>ex vivo</I> imaging showed high accumulation of FA-PLGA-Pba NPs in tumor site during 24 h after intravenous injection to MKN28 tumor-bearing mice model. These results demonstrate that our FA-PLGA-Pba NPs are useful for tumor-targeted delivery of PS for cancer treatment by PDT.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Folate-modified PLGA nanoparticles (FA-PLGA-Pba NPs) were developed with non-toxic materials. </LI> <LI> FA-PLGA-Pba NPs were stable in aqueous condition for long time without aggregation. </LI> <LI> FA-PLGA-Pba NPs killed cancer cells effectively upon laser irradiation, and showed superior tumor-targeting <I>invivo</I>. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>