We examine whether equity-linked private securities offerings are used as a mechanism for tunneling among firms that belong to a Korean chaebol. We find that chaebol issuers involved in intragroup ...deals set the offering prices to benefit their controlling shareholders. We also find that chaebol issuers (member acquirers) realize an 8.8% (5.8%) higher (lower) announcement return than do other types of issuers (acquirers) if they sell private securities at a premium to other member firms, and if the controlling shareholders receive positive net gains from equity ownership in issuers and acquirers. These results are consistent with tunneling within business groups.
In the problem Mix(H) one is given a graph G and must decide if the Hom-graph Hom(G,H) is connected. We show that if H is a triangle-free reflexive graph with at least one cycle, Mix(H) is ...coNP-complete. The main part of this is a reduction to the problem NonFlat(H) for a simplicial complex H, in which one is given a simplicial complex G and must decide if there are any simplicial maps ϕ from G to H under which some 1-cycles of G maps to homologically nontrivial cycle of H. We show that for any reflexive graph H, if the clique complex H of H has a free, nontrivial homology group H1(H), then NonFlat(H) is NP-complete.
The half-bridge (HB) LLC converter is one of the most attractive dc-dc converters for medium power supplies due to its soft switching capability. However, its conversion efficiency is considerably ...degraded in wide-link-voltage applications because of a small magnetizing inductance and wide switching frequency variation for a high voltage gain. In this paper, a boost power factor correction (PFC) stage, which can also play an important role during the hold-up time, is proposed for a high-efficiency HB LLC converter. In the proposed PFC stage, the boost PFC converter can be effectively utilized as a HB converter by replacing a boost diode and inductor with a synchronous switch and transformer, respectively. After the ac line is lost, the proposed PFC stage can operate as the HB converter and regulate the output voltage instead of the HB LLC converter. Thus, it enables the HB LLC converter to be designed with a large magnetizing inductance and narrow switching frequency variation. As a result, the proposed PFC stage can enhance the overall efficiency of the PSU by improving the efficiency of the HB LLC converter. To confirm the validity of this paper, a prototype with 180-264-Vrms ac line, 250-400-V link voltage, and 48 V/480 W output is tested.
Chiral metamaterials comprise a promising platform for advanced optoelectronic and biomedical applications. However, conventional fabrication via lithography is limited by its complexity and high ...cost. Herein, the lithography‐free fabrication of terahertz chiral metamaterials and their enhancement for sensing the chirality of biocrystal enantiomers is presented. Chiral Au microstrip patterns (CHAMs) in a saw‐tooth shape are fabricated by combining two‐step buckling processes and glancing‐angle deposition. Non‐superimposable geometric chirality is achieved by controlling the tilt angle between the asymmetric and biaxial strain axes and the selective area deposition of the Au layers by using the shadow effect. The manufactured chiral metamaterials show mirror‐shaped terahertz circular dichroism (TCD) signals in the range of 0.2–2.5 THz. Coupling of the induced electric and magnetic dipoles to the chiral‐shaped Au surfaces results in effective optical chirality enhancement. Finite‐difference time‐domain computational simulations reveal the homogeneous distribution of optical chirality with an absolute maximum of 2.24 in the near field. Summing the TCD signals for enantiomeric cystine biocrystals onto the chiral metamaterials shows an ≈7‐fold amplification in magnitude. This enhancement can be attributed to the synergistic effects of superchiral field enhancement and the electromagnetic resonance between the CHAMs and biocrystals.
3D chiral Au microstrip patterns are fabricated by combining a two‐step buckling process and glancing‐angle deposition. Terahertz circular dichroism measurements with enantiomeric biocrystals show a significant increase in peak intensity sevenfold greater than the control. This is attributed to the synergistic effects of the superchiral field and electromagnetically induced resonances between the chiral metamaterials and biocrystals.
Abstract Efficient sodium ion storage in graphite is as yet unattainable, because of the thermodynamic instability of sodium ion intercalates–graphite compounds. In this work, sodium fluorozirconate ...(Na 3 ZrF 7 , SFZ) functionalized graphite (SFZ‐G) is designed and prepared by the in situ mechanochemical silicon (Si) replacement of sodium fluorosilicate (Na 2 SiF 6 , SFS) and functionalization of graphite at the same time. During the mechanochemical process, the atomic Si in SFS is directly replaced by atomic zirconium (Zr) from the zirconium oxide (ZrO 2 ) balls and container in the presence of graphite, forming SFZ‐G. The resulting SFZ‐G, working as an anode material for sodium ion storage, shows a significantly enhanced capacity of 418.7 mAh g −1 at 0.1 C‐rate, compared to pristine graphite (35 mAh g −1 ) and simply ball‐milled graphite (BM‐G, 200 mAh g −1 ). In addition, the SFZ‐G exhibits stable sodium‐ion storage performance with 86% of its initial capacity retention after 1000 cycles at 2.0 C‐rate.
In this paper, a new single-stage half-bridge (HB) resonant <inline-formula><tex-math notation="LaTeX">LLC </tex-math></inline-formula> converter additionally employing one resonant capacitor and two ...relays with one package is proposed, compared with a single-stage HB <inline-formula><tex-math notation="LaTeX">LLC</tex-math></inline-formula> converter. Moreover, a center-tapped transformer is replaced with a coupled transformer. Since the proposed converter changes the turns ratio of the coupled transformer using a relay according to low- or high-input-voltage range, it can decrease the range of its needed voltage gain. It means that the proposed converter can be designed with large transformer magnetizing inductance compared with the conventional single-stage HB <inline-formula> <tex-math notation="LaTeX">LLC</tex-math></inline-formula> converter. As a result, the primary conduction and turn-off losses are reduced. Moreover, in low input voltage range, it has smaller total primary wire resistance of the transformer due to parallel connection of the coupled transformer, which decreases its conduction loss. In addition, additionally employed small-sized components can be inserted to the conventional system. To confirm the operation, features, and validity of the proposed converter, universal input with low line and high line and 16.5 V/60 W output laboratory prototype targeting laptop adapters with wide-input-voltage range is built and tested.
Global climate change accompanied by continuous increases in atmospheric carbon dioxide (CO2) concentration and temperature affects the growth and yield of important crops. The present study ...investigated the effect of elevated temperature and CO2 concentrations on the growth, yield, and photosynthesis of potato (Solanum tuberosum L. cv. Superior) crops using Korean Soil-Plant-Atmosphere-Research chambers that allow the regulation of temperature and CO2 concentration under daylight conditions. Based on the average temperature from 1991 to 2010 in the Jeonju area, South Korea, potato plants were exposed to four different conditions: ambient weather (400 μmol mol-1, aCaT), elevated temperature (+4°C, aCeT), elevated CO2 concentration (800 μmol mol-1, eCaT), and concurrently elevated CO2 concentration and temperature (eCeT). Under aCeT conditions, the temperature exceeded the optimal growth temperature range towards the late growth phase that decreased stomatal conductance and canopy net photosynthetic rate and subsequently reduced biomass and tuber yield. Stomatal conductance and chlorophyll concentration were lower under eCaT conditions than under aCaT conditions, whereas late-growth phase biomass and tuber yield were greater. Compared to other conditions, eCeT yielded a distinct increase in growth and development and canopy net photosynthetic rate during tuber initiation and bulking. Consequently, biomass and canopy net photosynthesis increased, and tuber yield increased by 20.3%, which could be attributed to the increased tuber size, rather than increased tuber number. Elevated CO2 reduced chlorophyll, magnesium, and phosphorus concentrations; reducing nitrogen concentration (by approximately 39.7%) increased the C:N ratio. The data indicate that future climate conditions will likely change nutrient concentration and quality of crops. The present study shows that while elevated temperature may negatively influence the growth and yield of potato crops, especially towards the late-growth phase, the concurrent and appropriate elevation of CO2 and temperature could promote balanced development of source and sink organs and positively effect potato productivity and quality.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Due to climate change, soil moisture may increase, and outflows could become more frequent, which will have a considerable impact on crop growth. Crops are affected by soil moisture; thus, soil ...moisture prediction is necessary for irrigating at an appropriate time according to weather changes. Therefore, the aim of this study is to develop a future soil moisture (SM) prediction model to determine whether to conduct irrigation according to changes in soil moisture due to weather conditions. Sensors were used to measure soil moisture and soil temperature at a depth of 10 cm, 20 cm, and 30 cm from the topsoil. The combination of optimal variables was investigated using soil moisture and soil temperature at depths between 10 cm and 30 cm and weather data as input variables. The recurrent neural network long short-term memory (RNN-LSTM) models for predicting SM was developed using time series data. The loss and the coefficient of determination (R
) values were used as indicators for evaluating the model performance and two verification datasets were used to test various conditions. The best model performance for 10 cm depth was an R
of 0.999, a loss of 0.022, and a validation loss of 0.105, and the best results for 20 cm and 30 cm depths were an R
of 0.999, a loss of 0.016, and a validation loss of 0.098 and an R
of 0.956, a loss of 0.057, and a validation loss of 2.883, respectively. The RNN-LSTM model was used to confirm the SM predictability in soybean arable land and could be applied to supply the appropriate moisture needed for crop growth. The results of this study show that a soil moisture prediction model based on time-series weather data can help determine the appropriate amount of irrigation required for crop cultivation.
Recently, the various types of the half-bridge (HB) converters with the output inductor have been developed, and they exhibit a good performance in medium power applications such as the server power ...supplies and personal computer power supplies requiring high output current. However, they have common problems such as the primary and secondary switch turn-off losses and snubber loss in the secondary side caused by the output inductor, which degrades light load efficiency. To relieve these limitations of the conventional HB converters, a new HB converter, which employs one additional switch and capacitor in the secondary side, is proposed for a high efficiency under light load conditions in this paper. Since the proposed converter operates like the HB LLC converter with below operation by turning on additional switch under light load conditions, the switch turn-off losses and snubber loss can be minimized, and the zero-voltage switching (ZVS) capability can be improved. Consequently, the proposed converter can achieve a high efficiency under light load conditions. To confirm the operation, features, and validity of the proposed converter, a 330-400 V input and 12 V/300 W output laboratory prototype is built and tested.
In this paper, a simple control method of the half-bridge (HB) LLC converter with one additional switch and capacitor in the primary side is proposed for wide-input-voltage applications with the ...hold-up time conditions. At nominal input, since the proposed method enables the HB LLC converter to operate with large transformer magnetizing inductance, it can reduce the conduction and switch turn-off losses in the primary side, which makes it highly efficient. On the other hand, during the hold-up time, since the proposed method increases the resonant capacitance by turning on one additional switch, the HB LLC converter can obtain high-voltage gain. To confirm the validity of the HB LLC converter with the proposed method, a 325-385 V input and 56 V/350 W output laboratory prototype is built and tested.
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