• Journal of Korea Trade
• /
• v.24 no.4
• /
• pp.1-17
• /
• 2020

Purpose - Since China has been South Korea's biggest export destination, uncertainty shocks originating from it would influence South Korea's exports. This paper evaluates the effects of China's economic policy uncertainty on Korea's exports to explore the transmission channels. Design/methodology - Incorporating endogeneities and nonlinearities, this study employs a quarterly time-varying parameters vector autoregressive model to investigate the relationships between China's economic policy uncertainty and Korea's exports, where the overparameterization due to time-varying specifications is overcome by a novel stochastic model specification search framework. According to previous theoretical studies, this paper assesses two channels, demand shock channel and exchange rate channel, through which foreign uncertainty affects Korea's exports. This paper identifies the primary drivers of Korea's aggregate exports and analyzes the rationales for the time-variant impacts of China's economic policy uncertainty on Korea's exports to China. Findings - Our empirical results reveal that Korea's aggregate exports are less responsive to China's economic policy uncertainty shocks and significantly move together with global demand. In contrast, its bilateral exports to China are highly responsive in a negative and time-variant way. Moreover, Chinese investment is an important channel through which China's economic policy uncertainty affects Korea's exports to China after 2010. Further, the time-variant effects of China's economic policy uncertainty on Korea's exports to China are related to changes in China's foreign trade policies, global economic conditions, and China's degree of economic freedom. Originality/value - Few previous studies touch the effects of external uncertainty shocks on South Korea's exports. This paper attempts to fill this gap and explicitly investigate the impacts of China's economic policy uncertainty on Korea's exports from a time-varying perspective. As Korea is an export-oriented economy, this study provides insights for the Korean government to understand the transmissions of external uncertainty better.

• Journal of Periodontal and Implant Science
• /
• v.52 no.2
• /
• pp.170-180
• /
• 2022

Purpose: This study was conducted to assess the effect of hard and/or soft tissue grafting on immediate implants in a preclinical model. Methods: In 5 mongrel dogs, the distal roots of P2 and P3 were extracted from the maxilla (4 sites in each animal), and immediate implant placement was performed. Each site was randomly assigned to 1 of the following 4 groups: i) gap filling with guided bone regeneration (the GBR group), ii) subepithelial connective tissue grafting (the SCTG group), iii) GBR and SCTG (the GBR/SCTG group), and iv) no further treatment (control). Non-submerged healing was provided for 4 months. Histological and histomorphometric analyses were performed. Results: Peri-implant tissue height and thickness favored the SCTG group (height of periimplant mucosa: 1.14 mm; tissue thickness at the implant shoulder and ±1 mm from the shoulder: 1.14 mm, 0.78 mm, and 1.57 mm, respectively; median value) over the other groups. Bone grafting was not effective at the level of the implant shoulder and on the coronal level of the shoulder. In addition, simultaneous soft and hard tissue augmentation (the GBR/SCTG group) led to a less favorable tissue contour compared to GBR or SCTG alone (height of periimplant mucosa: 3.06 mm; thickness of peri-implant mucosa at the implant shoulder and ±1 mm from the shoulder: 0.72 mm, 0.3 mm, and 1.09 mm, respectively). Conclusion: SCTG tended to have positive effects on the thickness and height of the periimplant mucosa in immediate implant placement. However, simultaneous soft and hard tissue augmentation might not allow a satisfactory tissue contour in cases where the relationship between implant position and neighboring bone housing is unfavorable.

• Journal of IKEEE
• /
• v.26 no.4
• /
• pp.553-559
• /
• 2022

In this paper, RC snubber circuit design technology for oscillation suppression in half-bridge configuration of cascode gallium nitride (GaN) field effect transistors (FETs) is analyzed. A typical wide band-gap (WBG) device, cascode GaN FET, has excellent high-speed switching characteristics. However, due to such high-speed switching characteristics, a false turn-off problem is caused, and an RC snubber circuit is essential to suppress this. In this paper, the commonly used experimental-based RC snubber design technique and the RC snubber design technique using the root locus method are compared and analyzed. In the general method, continuous circuit changes are required until the oscillation suppression performance requirement is met based on experimental experience . However, in root locus method, the initial value can be set based on the non-oscillation R-C map. To compare the performance of the two aforementioned design methods, a simulation experiment and a switching experiment using an actual double pulse circuit are performed.

• Steel and Composite Structures
• /
• v.46 no.4
• /
• pp.451-469
• /
• 2023

The use of precast hollow-core slabs (PCHCS) in civil construction has been increasing due to the speed of execution and reduction in the weight of flooring systems. However, in the literature there are no studies that present a finite element model (FEM) to predict the load-slip relationship behavior of pushout tests, considering headed stud shear connector and PCHCS placed at the upper flange of the downstand steel profile. Thus, the present paper aims to develop a FEM, which is based on tests to fill this gap. For this task, geometrical non-linear analyses are carried out in the ABAQUS software. The FEM is calibrated by sensitivity analyses, considering different types of analysis, the friction coefficient at the steel-concrete interface, as well as the constitutive model of the headed stud shear connector. Subsequently, a parametric study is performed to assess the influence of the number of connector lines, type of filling and height of the PCHCS. The results are compared with analytical models that predict the headed stud resistance. In total, 158 finite element models are processed. It was concluded that the dynamic implicit analysis (quasi-static) showed better convergence of the equilibrium trajectory when compared to the static analysis, such as arc-length method. The friction coefficient value of 0.5 was indicated to predict the load-slip relationship behavior of all models investigated. The headed stud shear connector rupture was verified for the constitutive model capable of representing the fracture in the stress-strain relationship. Regarding the number of connector lines, there was an average increase of 108% in the resistance of the structure for models with two lines of connectors compared to the use of only one. The type of filling of the hollow core slab that presented the best results was the partial filling. Finally, the greater the height of the PCHCS, the greater the resistance of the headed stud.

• Korean Journal of Agricultural Science
• /
• v.49 no.4
• /
• pp.771-783
• /
• 2022

In this study, the feasibility of alternative tractor Roll Over Protective Structure (ROPS) designed to evaluate conditions required for testing was confirmed. In accordance with Organization for Economic Cooperation and Development (OECD) code 4, the required load energy of the tractor ROPS was determined. First, the tractor ROPS test was performed and a repeated test was performed using a simplified ROPS as an alternative tractor ROPS. The test procedure is first rearward, second lateral, and last forward based on ROPS. The load test device consists of a load cell that measures force and a LVDT that measures deformation. Precision was confirmed by calculating the relative standard deviation of the simplified ROPS repeated test. Accuracy was analyzed by calculating the mean relative error between the mean measured values in the simplified ROPS test and the tractor ROPS test. As a result, the relative standard deviation was less than 2.5% for force and 3.3% for maximum deformation overall, showed the highest precision in lateral load. The mean relative error value for force measured at the lateral load of simplified ROPS was 0.5%, showing the highest accuracy. In the front load test, the mean relative error of maximum deformation was 20.5%, showing the lowest accuracy. The mean relative error (MRE) was high in the forward load test was because of structural factors of the ROPS. The simplified ROPS model is expected to save money and time spent preparing tractors.

• Journal of Korea Trade
• /
• v.27 no.3
• /
• pp.179-198
• /
• 2023

Purpose - There is a paucity of literature dealing with exporters' compliance issues in e-commerce exports. This study aims to fill this gap in the literature by exploring customs initiatives to facilitate the e-commerce exports of small and medium-sized enterprises (SMEs) in the changed compliance environment. The central question of this study was divided into five subquestions: first regarding the pros and cons of trade facilitation measures for Korean e-commerce export clearance; second and third questions about risk and compliance management for facilitation fourth about instruments, the changes in Korean SME compliance burden in e-commerce exports, and ways to improve trade facilitation for e-commerce exports. Design/methodology - This study adopts a qualitative approach using a case study method to understand the SME experience in Korean e-commerce export compliance procedures. A qualitative method was selected to answer research questions requiring an in-depth understanding of the regulatory procedures of customs administration and exporters' compliance burden. Because this study addresses the changing compliance environment for which statistical data is insufficient, a quantitative method is considered inappropriate. Based on the approach, data were collected using multiple sources, including an extensive literature review, interviews, and field observations. Thematic pattern matching was applied to interpret the data. Findings - This study examined ways to support SMEs in the changed e-commerce export compliance environment. Facilitation measures for e-commerce exports have contributed to SME access to global markets, simplifying export clearance procedures, and saving exporters' compliance costs. However, such instruments are limited in promoting SME compliance capabilities to cope with intensified competition and strengthened controls over foreign exporters in cross-border e-commerce. Therefore, this study highlights the importance of reshaping facilitation measures for e-commerce exports based on risk and compliance management theories to a system encouraging exporters' voluntary compliance. Originality/value - This study's academic significance derives from verifying the relationship between trade facilitation instruments and risk and compliance management procedures using an actual case in Korea. It is also of practical importance in navigating the directions for improving facilitation measures for e-commerce exports in a changed compliance environment.

• Journal of the Korean Wood Science and Technology
• /
• v.51 no.5
• /
• pp.334-344
• /
• 2023

Dregs from the sugar palm (Arenga pinnata) starch industry are considered a waste product of the agricultural industry and have not yet been optimally utilized. Therefore, this study aimed to manufacture particleboards from dregs using different amounts of adhesive and particle size ratios. Sugar palm dregs, which had been separated into fibers and powder/fine particles, were used as raw material for making particleboards. The fiber had an average length of 6.84 ± 3.23 cm, while the fine particles were of a size that passed through size 10 mesh and remained in size 60 mesh. Three ratios of fiber to fine particles (100:0, 75:25, and 50:50 wt%) with three different amounts of sucrose-citric acid adhesive (10, 15, and 20 wt%) were used in this study. Increasing the amount of fine particles and the resin content can improve the physical properties and the internal bond strength of boards made from sugar palm dregs. The fine particles possibly filled the gap between the fibers in the particleboard, while the fibers exhibited a high bending strength. As a result, a high-performance particleboard can be attained by combining the composition ratio of fiber/fine particles and resin content. In this study, particleboards made from fiber/fine particles (75:25 wt%) and adhesive content of 15 wt% and 20 wt% had the mechanical properties that met the requirements of Japanese Industrial Standard (JIS) A 5908 type 18. Sugar palm dregs have the potential to be used as raw materials to create value-added particleboards.

• Progress in Superconductivity
• /
• v.4 no.1
• /
• pp.1-9
• /
• 2002

Transferring single flux quanta across a Josephson junction at an exactly determined rate has made highly precise voltage measurements possible. Making use of self-shunted Nb-based SINIS junctions, programmable fast-switching DC voltage standards with output voltages of up to 10 V were produced. This development is now extended from fundamental DC measurements to the precise determination of AC voltages with arbitrary waveforms. Integrated RSFQ circuits will help to replace expensive semiconductor devices for frequency control and signal coding. Easy-to-handle AC and inexpensive quantum voltmeters of fundamental accuracy would be of interest to industry. In analogy to the development in the flux regime, metallic nanocircuits comprising small-area tunnel junctions and providing the coherent transport of single electrons might play an important role in quantum current metrology. By precise counting of single charges these circuits allow prototypes of quantum standards for electric current and capacitance to be realised. Replacing single electron devices by single Cooper pair circuits, the charge transfer rates and thus the quantum currents could be significantly increased. Recently, the principles of the gate-controlled transfer of individual Cooper pairs in superconducting A1 devices in different electromagnetic environments were demonstrated. The characteristics of these quantum coherent circuits can be improved by replacing the small aluminum tunnel Junctions by niobium junctions. Due to the higher value of the superconducting energy gap ($\Delta_{Nb}$ ＝ $7\Delta_{Al}$), the characteristic energy and the frequency scales for Nb devices are substantially extended as compared to A1 devices. Although the fabrication of small Nb junctions presents a real challenge, the Nb-based metrological devices will be faster and more accurate in operation. Moreover, the Nb-based Cooper pair electrometer could be coupled to an Nb single Cooper pair qubit which can be beneficial for both, the stability of the qubit and its readout with a large signal-to-noise ratio..

• Journal of Korea Trade
• /
• v.26 no.7
• /
• pp.109-126
• /
• 2022

Purpose - Based on the relevant panel data for China and 13 of the RCEP countries from 2008-2019, this paper conducts an in-depth study on the impact of trade facilitation levels on China's cross-border e-commerce exports using the expanded trade gravity model. Design/methodology - This study constructs a trade facilitation index (TFI) system, and uses the principal component analysis method to measure the trade facilitation levels of RCEP countries in 2008-2019. This result is then introduced into the extended gravity model to explore the effect of trade facilitation in RCEP countries on China's cross-border e-commerce export. Findings - It is found that the overall trade facilitation level has a significant effect on China's cross-border e-commerce exports. Among the primary indicators, with the exception of infrastructure, the other four indicators demonstrate a significant impact. The findings show that China should strengthen its cooperation with RCEP countries in trade facilitation and cross-border e-commerce to better achieve complementary regional economic development. Originality/value - This paper has three contributions: first, this paper builds a TFI system that includes five primary indicators based on the characteristics of cross-border e-commerce. Second, we explore the impact of trade facilitation levels of RCEP countries on China's cross-border e-commerce exports, which helps to fill the gap in existing studies of the impact of cross-border e-commerce exports. Third, this paper further analyzes the impact of five primary indicators on cross-border e-commerce exports; this thus provides more targeted measures to improve trade facilitation levels.

• Journal of Drive and Control
• /
• v.20 no.2
• /
• pp.31-39
• /
• 2023

The aim of this study was to measure and analyze engine load factor (LF) according to working conditions (operation type and gear stage) of small agricultural multi-purpose cultivator to estimate the emission of air pollutants. To calculate LF, a torque sensor capable of collecting torque and rotational speed was installed on the engine output shaft and DAQ was used to collect data. A field test was conducted with major operation of a cultivator and tillage operations (plow tillage and rotary tillage). Engine power was calculated using engine torque and rotational speed and LF was calculated using real-time power and rated power. In addition, unified LF was calculated using the weight for each operation and the average LF for each operation. As a result, average LF values at 1.87 and 3.10 km/h by plow tillage were 0.50 and 0.69, respectively. Average LF values at 1.87 and 3.10 km/h by rotary tillage were 0.70 and 0.78, respectively. Furthermore, unified LF calculated in consideration of the weight factor showed a value of 0.65, which was 135% higher than the conventional LF (0.48). Results of this study could be used as basic information for realizing LF values in the field of agricultural machinery.