• The Journal of Asian Finance, Economics and Business
• /
• v.9 no.10
• /
• pp.1-13
• /
• 2022

This paper empirically explores the predicting ability of the newly proposed smooth transition (ST) time-varying combining forecast methods. The proposed method allows the "weight" of combining forecasts to change gradually over time through its unique feature of transition variables. Stock market returns from 7 countries were applied to Ad Hoc models, the well-known Generalized Autoregressive Conditional Heteroskedasticity (GARCH) family models, and the Smooth Transition Exponential Smoothing (STES) models. Of the individual models, GJRGARCH and STES-E&AE emerged as the best models and thereby were chosen for constructing the combined forecast models where a total of nine ST combining methods were developed. The robustness of the ST combining forecasts is also validated by the Diebold-Mariano (DM) test. The post-sample forecasting performance shows that ST combining forecast methods outperformed all the individual models and fixed weight combining models. This study contributes in two ways: 1) the ST combining methods statistically outperformed all the individual forecast methods and the existing traditional combining methods using simple averaging and Bates & Granger method. 2) trading volume as a transition variable in ST methods was superior to other individual models as well as the ST models with single sign or size of past shocks as transition variables.

• Nuclear Engineering and Technology
• /
• v.54 no.3
• /
• pp.877-887
• /
• 2022

A new reactor concept is described that directly couples a supercritical CO₂ (sCO₂) power cycle with a CO₂-cooled, heavy water moderated pressure tube core. This configuration attains the simplification and economic potential of past direct-cycle sCO₂ concepts, while also providing safety and power density benefits by using the moderator as a heat sink for decay heat removal. A 200 MWe design is described that heavily leverages existing commercial nuclear technologies, including reactor and moderator systems from Canadian CANDU reactors and fuels and materials from UK Advanced Gas-cooled Reactors (AGRs). Descriptions are provided of the power cycle, nuclear island systems, reactor core, and safety systems, and the results of safety analyses are shown illustrating the ability of the design to withstand large-break loss of coolant accidents. The resulting design attains high efficiency while employing considerably fewer systems than current light water reactors and advanced reactor technologies, illustrating its economic promise. Prospects for the design are discussed, including the ability to demonstrate its technologies in a small (~20 MWe) initial system, and avenues for further improvement of the design using advanced technologies.

• Journal of the Korean Solar Energy Society
• /
• v.32 no.spc3
• /
• pp.275-281
• /
• 2012

Proton Exchange Membrane Fuel Cells (PEMFC) are the most appropriate for energy source of small robot applications. PEMFC has superior in power density and thermodynamic efficiency as compared with the Direct Methaol Fuel Cell (DMFC). Furthermore, PEMFC has lighter weight and smaller size than DMFC which are very important factors as small robot power system. The most significant factor of mobile robots is weight which relates closely with energy consumption and robot operation. This research tried to find optimum specifications in terms of type, number of cell, active area, cooling method, weight, and size. In order to find optimum 500W PEMFC, six options are designed in this paper and studied to reduce total stack weight by applying new materials and design innovations. However, still remaining problems are thermal management, robot space for energy sources, and soon. For a thermal management, design options need to analysis of Computational Fluid Dynamics (CFD) for determining which option has the improved performance and durability.

• Korean journal of applied entomology
• /
• v.54 no.2
• /
• pp.127-136
• /
• 2015

We report new host records of four ichneumonids from Korea. They were discovered from the pupae of Apatura metis Frever (Lepidoptera: Nymphalidae), Allotraeus sphaerioninus Bates (Coleoptera: Cerambycidae) and Ivela auripes (Butler) (Lepidoptera: Lymantriidae) respectively. Diagnoses, illustrations, host records of the four species, and a list of ichneumon species parasitizing of I. auripes are provided.

• 한국태양에너지학회:학술대회논문집
• /
• 2012.03a
• /
• pp.211-216
• /
• 2012

Proton Exchange Membrane Fuel Cells (PEMFC) are the most appropriate for energy source of small robot applications. PEMFC has superior in power density and thermodynamic efficiency as compared with the Direct Methaol Fuel Cell (DMFC). Furthermore, PEMFC has lighter weight and smaller size than DMFC which are very important factors as small robot power system. The most significant factor of mobile robots is weight which relates closely with energy consumption and robot operation. This research tried to find optimum specifications in terms of type, number of cell, active area, cooling method, weight, and size. In order to find optimum 500W PEMFC, six options are designed in this paper and studied to reduce total stack weight by applying new materials and design innovations. However, still remaining problems are thermal management, robot space for energy sources, and so on. For a thermal management, design options need to analysis of Computational Fluid Dynamics (CFD) for determining which option has the improved performance and durability.

• Journal of the Korean Solar Energy Society
• /
• v.34 no.4
• /
• pp.17-22
• /
• 2014

The design of a fuel cells stack is important to get optimal output power. This study focuses on the evaluation of fuel cell system for unmaned aerial vehicles (UAVs). Low temperature proton exchange membrane (LTPEM) fuel cells are the most promising energy source for the robot applications because of their unique advantages such as high energy density, cold startup, and quick response during operation. In this paper, a 600 W open cathode LTPEM fuel cell was tested to evaluate the performance and to determine optimal operating conditions. The open cathode design reduces the overall size of the system to meet the requirement for robotic application. The cruise power requirement of 600 W was supported entirely by the fuel cell while the additional power requirements during takeoff was extended using a battery. A peak of power of 900 W is possible for 10 mins with a lithium polymer (LiPo) battery. The system was evaluated under various load cycles as well as start-stop cycles. The system response from no load to full load meets the robot platform requirement. The total weigh of the stack was 2 kg, while the overall system, including the fuel processing system and battery, was 4 kg.

• The Korean Journal of Mycology
• /
• v.27 no.3 s.90
• /
• pp.208-210
• /
• 1999

Three species belong to the genus Laboulbenia were collected on Carabidae (Coleoptera) and Harpalidae (Coleoptera) from several regions of Korea. Laboulbenia anoplogenii Thaxter was collected from Stenolophus quinquepustulatus Widemann. The characters of this species are the fourth layer of receptacle consisted of two or three cells and the distal end of its posterior cell projecting upward. The thalli were produced on posterior and anterior legs of the hosts. Laboulbenia habui Terada was collected from Chlaenius variicornis Bates. This species is characterized by the basal cells of the secondary appendage composed of short-cylindrical cells, arranged alternately on a double row. The thalli were produced from the elytra and anterior abdomen of the hosts. Laboulbenia pallida Thaxter was collected from Anisodactylus signatus Panzer. This species is distinguished from other related species by the rounded tip of perithecium and the outer appendage branched on the basal cell. The thalli were produced on the posterior elytra of the hosts.

• Korean journal of applied entomology
• /
• v.27 no.1
• /
• pp.21-27
• /
• 1988

A study was carried out to investigate the morphological characteristics and life histories of H. morosa and H. diomPhalia during the period from 1984 to 1986. The head capsule width and bOdy length of H. Morosa larvae were slightly greater than those of H. diomPhalia. Otherwise, the two species looked very similar and were hard to be differentiated from each other in all life stages. H. morosa adults emerged in late June and laid eggs in soil during the period between mid July and mid August. Larvae developed by September to the last(3rd) instar which overwintered to pupate in late May. H. diomPhalia adults emerged from mid August but remained under the soil until next spring after which females laid eggs in soil from late May to early July. Larvae developed in most cases to the last instar by September and overwintered thereafter. Unlike H. morosa, they resumed feeding next April and began to pupate in late July. The egg periods of H. morosa and H. diomPhalia did not significantly differ but the larval and pupal periods of the latter were longer than those of the former.

• Korean journal of applied entomology
• /
• v.27 no.4
• /
• pp.194-199
• /
• 1988

The seasonal movements of Holotrichia morosa and H. diomphalia in soil were investigated during the period from 1984 to 1986 in Suwon. Most cf the eggs, active larvae and adults of the two species could be found at the soil depth of I-IDem. The larvae began downward movement in late October and early November in order for overwintering when soil tempe¬rature at 5cm below ground reached about $10^{\circ}C$. The overwintering depths of the larvae were 10-40cm for H. morosa and 30-80cm for H. diomPhalia. After the overwintering, pupation and adult emergence of H. morosa occurred at the overwintered sites, \vhereas H. diomPhalia larvae returned to near soil surface next April, and resumed feeding. H.diomphalia larvae began to move downward again in late June for pupation and adult emergence, and overwintered thereafter as adults at the depth of 1O-40cm.

• Journal of Ginseng Research
• /
• v.12 no.1
• /
• pp.47-52
• /
• 1988

In order to establish the integrated management of white grubs in ginseng field damages of ginseng plants (Panax ginseng C.A. Meyer) by the larvae of the larger black chamfer (Holotrichia morose Waterhouse) and the Korean black chamfer (Holotrichia diomphalia Bates) were investigated. Most of ginseng damages due to H, morose usually occurred in September through October, mainly on 2nd year plants. However, the damage by H. diomphalia occurred in September through October (usually in odd number of years) on 2nd year plants and in the following May and June on 3rd year plants. Therefore, in the fall of every odd number of years, synchronized occurrence of the two species caused severe damage on ginseng plants. Both of the 3rd instar larvae of the forementioned two species damaged ginseng roots regardless of the age of the plants when ginseng plants were artificially infested with them. Ginseng fields located at the slopes with good drainage are most likely damaged by them.