Family Control Firms and Real Earnings Management: The Case of Korean Chaebols

Tabi Frankcline Tambe,심호석 글로벌경영학회 2017 글로벌경영학회지 Vol.14 No.6

We examine the relation between family control firms and real earnings management. Specifically, we see how much family control firms engage in real earnings management compared to non-family control firms. With a sample of 1290 Korean listed family control firms in KOSPI and KOSDAQ market during 2005-2015, we conduct regression analysis to compare real earnings management between family control firms and non-family control firms. We find that family control firms, on average, do not engage in income-increasing real earnings management, compared to a sample of 1283 non-family control firms. Instead, our empirical results show that family control firms, on average, conduct income-decreasing real earnings management compared to non-family control firms, consistent with the results of previous studies that show income-decreasing earnings management with accruals in Korea. we also find in further analysis that family control firms meet or beat earnings benchmarks(zero earnings and last year earnings) less than non-family control firms. We interpret these results as family control firms place more importance on long-term persistence rather than short-term performance. We contribute to accounting literature by adding evidence on the behavior of real earnings management of Chaebol firms in Korea.

High performance p-type chlorinated-benzothiadiazole-based polymer electrolyte gated organic field-effect transistors

Tabi, Grace Dansoa,Nketia-Yawson, Benjamin,Kang, So-Huei,Yang, Changduk,Noh, Yong-Young Elsevier 2018 ORGANIC ELECTRONICS Vol.54 No.-

<P><B>Abstract</B></P> <P>We report the evaluation of charge transport parameters of four p-type dichlorinated-2,1,3-benzothiadiazole (2ClBT) based conjugated polymers end-capped with different electron-donor units (thiophene (T), thieno[3,2-<I>b</I>]thiophene (TT), 2,2′-bithiophene (DT), and (E)-2-(2-(thiophen-2-yl)vinyl)thiophene (TVT)) in electrolyte gated organic field-effect transistors operating at a driving voltage of −2 V. Remarkable hole mobility improvement of 0.13–0.56 cm<SUP>2</SUP>V<SUP>−1</SUP>s<SUP>−1</SUP> were achieved in 2ClBTs based polymers, with P2ClBT-DT recording the highest mobility of 0.56 cm<SUP>2</SUP>V<SUP>−1</SUP>s<SUP>−1</SUP> and current on/off ratio ∼10<SUP>7</SUP>. Interestingly, a positive threshold voltage shift (Δ<I>V</I> <SUB>Th</SUB>) was observed in the transfer characteristics from the linear to saturation regime of all the 2ClBTs based polymer electrolyte gated OFET devices of <I>L</I> = 10 μm, contrary to devices with conventional poly(methyl methacrylate) gate dielectric, which showed a negative Δ<I>V</I> <SUB>Th</SUB> shift. Among the 2ClBTs based polymers, P2ClBT-TVT devices showed the lowest mobility and Δ<I>V</I> <SUB>Th</SUB> shift, which is attributed to severe ion diffusion in the polymer semiconducting layer owing to the vinyl group backbone susceptible to electrochemical doping. Our results emphasize essential selection consideration of the monomeric moieties, molecular ordering, π-π stacking and backbone planarity of conjugated polymers for electrolyte based organic devices.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We report high performance benzothiadiazole based OFETs with solid state ion dielectrics. </LI> <LI> Remarkable hole mobility improvement of 0.13–0.56 cm<SUP>2</SUP>V<SUP>−1</SUP>s<SUP>−1</SUP> were achieved. </LI> <LI> Structure-property relationship mainly is discussed by using different electron-donor units. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

High performance p-type chlorinated-benzothiadiazole-based polymer electrolyte gated organic field-effect transistors

Tabi, Grace Dansoa,Nketia-Yawson, Benjamin,Kang, So-Huei,Yang, Changduk,Noh, Yong-Young Elsevier Science B.V., Amsterdam. 2018 Organic electronics Vol.2018 No.54

Improved Electron Transport in Ambipolar Organic Field-Effect Transistors with PMMA/Polyurethane Blend Dielectrics

Grace Dansoa Tabi,Benjamin Nketia-Yawson,조제웅,노용영 한국고분자학회 2020 Macromolecular Research Vol.28 No.13

We report improved electron transport in solution-processed ambipolar organic field-effect transistors (OFETs) employing polymer dielectric blends of low-k poly(methyl methacrylate) (PMMA) and polyurethane (PU) elastomer. Ambipolar poly(9,9-dioctylfluorene-alt-benzothiadiazole) (F8BT) OFETs typically showed an unbalanced hole and electron mobilities of 8.7 ± 0.4 × 10-4 and 2.0±0.1×10-4 cm2V-1s-1 respectively, using neat PMMA gate dielectric. By controlling the blending ratio of PU (0~50 v%) in the PMMA-PU blend dielectrics, we tuned the charge carrier transport in the F8BT OFETs. The electron mobility gradually increases significantly, resulting in nearly perfect ambipolar characteristics with hole and electron mobilities of 6.0 ±0.7× 10-4 and 9.7±0.4×10-4 cm2V-1s-1 respectively in PMMA: PU blend of 50:50 v%. The remarkable trend ensues from trapping of hole carriers at the dielectric/semiconductor by the -N-H- and carbonyl group (C=O) interface dipoles in the PU dielectric. The PMMA-PU blend dielectrics demonstrate excellent potentials for high-performance ambipolar OFETs, inverters, and complementary circuits.

Tribological properties of Ti-4Si-xZr-yY2O3/ 5TiO2 Composites Prepared by High-Energy Milling,Cold Pressing and Sintering

Vitus Mwinteribo Tabie,Xiaodong Shi,Jianwei Li,Chengbin Cai,Xiaojing Xu 한국정밀공학회 2019 International Journal of Precision Engineering and Vol.20 No.11

In the present study, tribological properties of Ti–4Si–xZr–yY2O3/5TiO2 were investigated. Four composites; Ti–4Si/5TiO2, Ti–4Si–1.3Zr/5TiO2, Ti–4Si–0.3Y2O3/5TiO2 and Ti–4Si–1.3Zr–0.3Y2O3/5TiO2 were fabricated by high-energy milling and cold pressing method. The composites showed enhanced wear and friction resistance against Si3N4 spheres counterface. The hardness and wear resistance of the composite increased with the addition of rare earth and Zirconium. Ti–4Si–1.3Zr–0.3Y2O3/5TiO2 composite has the smallest wear scar (222 μm) showing good wear resistance. Fatigue wear, supplemented by abrasive, oxidative and adhesive wears were identified as the predominant wear mechanisms. The study also found that rare earth Y2O3 can significantly improve the wear resistance of composites as it reduces the friction coefficient of Ti–4Si–1.3Zr/5TiO2 composite by about 25%.

Polymer Electrolyte Blend Gate Dielectrics for High-Performance Ultrathin Organic Transistors: Toward Favorable Polymer Blend Miscibility and Reliability

Nketia-Yawson, Benjamin,Tabi, Grace Dansoa,Noh, Yong-Young American Chemical Society 2019 ACS APPLIED MATERIALS & INTERFACES Vol.11 No.19

<P>We report on systematic mobility enhancements in electrolyte-gated organic field-effect transistors (OFETs) by thinning down the active layer and exploiting polymer solid-state electrolyte gate insulators (SEGIs). The SEGI is composed of homogeneous poly(vinylidene fluoride-<I>co</I>-hexafluoropropylene) [P(VDF-HFP)] polymer solution-ion gel blends of high areal capacitance of >10 μF cm<SUP>-2</SUP> at 1 Hz. By scaling up the poly(3-hexylthiophene) (P3HT) semiconducting layer by 1 order of magnitude (5-50 nm), an ultraviolet photoelectron spectroscopy examination reveals a downward vacuum-level shift generating a substantial hole injection barrier that originates from different interfacial dipole layer formations. The ultrathin (5.1 nm) P3HT FETs outperformed the other devices, exhibiting stable device characteristics with a highest field-effect mobility of >2 cm<SUP>2</SUP> V<SUP>-1</SUP> s<SUP>-1</SUP> (effective mobility of 0.83 ± 0.05 cm<SUP>2</SUP> V<SUP>-1</SUP> s<SUP>-1</SUP>), on/off ratio of ∼10<SUP>6</SUP>, low threshold voltage of <−0.6 V, and low gate-leakage current levels of ∼10<SUP>5</SUP> below the on-current levels in 10 μm channel length devices. We observed a positive threshold voltage shift in the P3HT/SEGI FETs with decreasing semiconductor thickness. The aforementioned mobility is at least 10 times greater than that of neat P(VDF-HFP) devices. The significant FET performance is attributed to a better insulator/semiconductor interface, efficient hole injection from the Au electrode resulting in a low contact resistance of <500 Ω cm, and boosted charge-carrier densities in the transistor channel. This work demonstrates an excellent approach for carrier mobility enhancement and reliability assessment in low-voltage-operated electrolyte-gated OFETs.</P> [FIG OMISSION]</BR>

Low-voltage operated solid-state electrolyte-gated ambipolar organic field-effect transistors

Nketia-Yawson, Benjamin,Tabi, Grace Dansoa,Noh, Yong-Young Elsevier Science B.V., Amsterdam. 2018 Organic electronics Vol.2018 No.52

Chlorinated 2,1,3-Benzothiadiazole-Based Polymers for Organic Field-Effect Transistors

Kang, So-Huei,Tabi, Grace Dansoa,Lee, Junghoon,Kim, Gyoungsik,Noh, Yong-Young,Yang, Changduk American Chemical Society 2017 Macromolecules Vol.50 No.12

<P>The vital role of introducing chlorine (Cl) atoms onto conjugated polymers, which affects their semiconducting properties, is not yet well understood. A series of donoracceptor polymers based on dichlorinated-2,1,3-benzothiadiazole (2ClBT) and four different donor moieties with various conjugation lengths (thiophene (T), thieno[3,2-b]thiophene (TT), 2,2'-bithiophene (DT), and (E)-2-(2-(thiophen-2-yl)vinyl)thiophene (TVT)) were synthesized and used in organic field-effect transistors (OFETs). The structureproperty relationship associated with the 2ClBT-based polymers was thoroughly investigated via a range of techniques, and it was found that a change in the conjugation length of the main backbone could alter energy levels, morphology, and optoelectronic properties, which had a significant effect on the charge transport property. P2CLBT-TVT exhibited superior qualities relative to the other samples with respect to the degree of uniform film-forming ability and molecular organization and charge carrier transport, which resulted in the best hole mobility of 0.147 cm(2) V-1 s(1). Furthermore, we also emphasize that for all the polymers no substantial changes were observed in the OFET transfer-curve slopes during 200 testing cycles, indicating excellent operational stability. This study demonstrates that the design of semiconducting polymers possessing Cl atoms was effective at improving operating stability in the OFETs manufactured from them.</P>

Effect of vacuum metalized gate electrode in top-gate solid-state electrolyte-gated organic transistors

Nketia-Yawson, Benjamin,Tabi, Grace Dansoa,Xu, Yong,Noh, Yong-Young Elsevier Science B.V., Amsterdam. 2018 ORGANIC ELECTRONICS Vol.2018 No.55

Effect of Garcinia kola seeds supplemented diet on growth performance and gonadal development of Oreochromis niloticus juveniles breed in ponds

Nyadjeu, Paulin,Angoun, Jeannette,Ndasi, Ngwasiri Pride,Tabi-Tomedi, Minette Eyango The Korean Society of Fisheries and Aquatic Scienc 2019 Fisheries and Aquatic Sciences Vol.22 No.9

Background: Despite the favorable geo-climatic potential of Cameroon, the national production of tilapia remains low due to poor tilapia growth reported by fish farmers. One of the underlying reasons is the early female maturation at a very small size and precocious breeding in earthen ponds, resulting in overpopulation which leads to stunted growth and therefore to the production of unmarketable fish size. Studies have shown that dietary supplementation of G. kola enhanced growth in young Clarias gariepinus and Oreochromis niloticus. It was also reported that G. kola inhibited spawning in Tilapia adult females. Therefore, this study sought to assess the effects of Garcinia kola as growth promoter and inhibitor of gonadal development in young Oreochromis niloticus. Methods: A total of 108 juveniles weighing $13.32{\pm}0.62g$ were randomly distributed in 9 hapas of 12 fishes each (9 females and 3 males) and fed for 70 days with three isonitrogenous diets, 40% crude protein with increasing Garcinia kola supplementation levels of 0 (normal diet), 6% and 10% (experimental diets). Physico-chemical parameters of the water (temperature, dissolved oxygen, pH, nitrate, nitrite, ammonia, and transparency) were measured twice a week. Every 14 days, fish were harvested, counted, and weighed. At the end of the experiment, three fish of each sex per replicate were sacrificed and their gonad and liver collected and weighed. Data were statistically analyzed using one-way analysis of variance repeated measure followed by Newman-Keuls multiple tests. Results: The results showed that all physico-chemical parameters of the water were within the recommended values for Tilapia culture. Tilapia fed 6% Garcinia kola supplemented diet displayed higher final body weight in males ($38.60{\pm}3.50g$) and females ($36.77{\pm}3.62g$) compared to those receiving normal diet ($36.23{\pm}1.36g$ and $25.87{\pm}3.32g$; respectively to the final body weight in males and females). The gonadosomatic index and hepatosomatic index indicated no significant variation in males while in females, these were significantly low in the experimental fish compared to control fish. Conclusion: The results of this study demonstrated that supplementation of G. kola seeds in diets of young Tilapia improved growth performance and impaired gonadal development in females.