• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.10 no.2
• /
• pp.173-179
• /
• 1998

An experimental study was conducted on the effect of compressor capacity control range of heat pump on the seasonal energy efficiency ratio with variation of the maximum and minimum compressor input frequencies. To obtain seasonal energy efficiency ratio, steady state test at the maximum, minimum and intermediate compressor speed and cyclic test at the minimum compressor speed should be conducted. Maximum input frequency was varied to 95Hz, 105Hz, and 115Hz, and the minimum input frequency was varied to 35Hz, 45Hz, and 55Hz. The seasonal energy efficiency ratio increased as the input frequency of the compressor decreased. The maximum input frequency had only slight effects on the SEER.

• Korean Journal of Remote Sensing
• /
• v.34 no.4
• /
• pp.639-647
• /
• 2018

This paper presents TerraSAR-X and KOMPSAT-5 sigma nought variation according to season and antenna observation configuration in Mongolia. Two types of landcover including bare surface and cropland were examined. The seasonal variation of sigma nought in cropland was about 7 dB and particularly a significant sigma nought reduction occurred after harvest. On the contrary, the Mongolia bare surface provides a consistent sigma nought values for several years with an annual variation less than 2.5 dB of standard deviation. However, the bare soil was relatively sensitive to look-direction (or ascending or descending mode) as well as incidence angle while the cropland was almost independent of antenna look-direction and small incidence angle changes. Although the look-directional variation of bare surface sigma nought was observed in this study, the look-direction anisotropic nature of the surface was not well examined. A further study would be required to account for this feature with various SAR observation configurations.

• Proceedings of the KSRS Conference
• /
• 2000.04a
• /
• pp.13-18
• /
• 2000

We observed sea level variation of the long time at Kerguelen island in the South Indian Ocean with ARGOS data and meteorological data during about 1 year(May 1993~March 1994) through using filter, spectral analysis, coherency and phase, and found characteristics for the two oceanic signal levels(detided oceanic signal level, h$_{detided}$ and seasonal oceanic level, h$_{corr.ib}$). The forms of variations are very well agreed to between ARGOS data and meteorological data for atmospheric pressure in the observed periods. The seasonal difference of sea level between Summer and Winter is about 1.6cm. Both the detided oceanic signal level(h$_{detided}$) variation and the inverted barometer level(h$_{ib}$) variation have a strong correlation for T>1day period bands. Characteristics of h$_{detided}$ variation are decided not by the influence of any meteorological distributions (pressure, winds, etc), but the influence of another factors(temperature, salinity, etc.) for T>2days periods bands. h$_{corr.ib}$ plays an very important role of sea level variation of the long time term(especially T>about 180days period bands).

• Journal of Environmental Science International
• /
• v.21 no.1
• /
• pp.23-30
• /
• 2012

The aerosol number concentration have measured with an aerodynamic particle sizer spectrometer(APS) at Gosan site in Jeju, Korea, from March 2010 to March 2011. And then the atmospheric aerosol number concentration, the temporal variation and the size distribution of aerosol number concentration have been investigated. The aerosol number concentration varies significantly from 748 particles/$cm^3$ to zero particles/$cm^3$. The average number concentration in small size ranges are very higher than those in large size ranges. The number concentrations in the size range 0.25~0.28 ${\mu}m$, 0.40~0.45 ${\mu}m$ and 2.0~2.5 ${\mu}m$ are about 84 particles/$cm^3$, 2 particles/$cm^3$ and 0.4 particles/$cm^3$, respectively. The number concentrations in range of larger than 7.5 ${\mu}m$ are below 0.001 particles/$cm^3$. The seasonal variations in the number concentration for smaller particle(<1.0 ${\mu}m$) are not much, but the variations for larger particle are very evident. And strong amplitudes of diurnal variations of entire averaged aerosol number concentration are not observed. Size-fractioned aerosol number concentrations are dramatically decreased with increased particle size. The size-fractioned aerosol number concentrations in size range 0.8~4.0 ${\mu}m$ during nighttime are evidently higher than during daytime, but similar levels are appeared in other size range. The seasonal differences in the size-fractioned number concentrations for smaller size range(<0.7 ${\mu}m$) are not observed, however, the remarkable seasonal differences are observed for larger size than 0.7 ${\mu}m$.

• The korean journal of orthodontics
• /
• v.47 no.5
• /
• pp.298-305
• /
• 2017

Objective: This paper describes changes in the characteristics of patients seeking orthodontic treatment over the past decade and the treatment they received, to identify any seasonal variations or trends. Methods: This single-center retrospective cohort study included all patients who presented to Seoul National University Dental Hospital for orthodontic diagnosis and treatment between January 1, 2005 and December 31, 2015. The study analyzed a set of heterogeneous variables grouped into the following categories: demographic (age, gender, and address), clinical (Angle Classification, anomaly, mode of orthodontic treatment, removable appliances for Phase 1 treatment, fixed appliances for Phase 2 treatment, orthognathic surgery, extraction, mini-plate, mini-implant, and patient transfer) and time-related variables (date of first visit and orthodontic treatment time). Time series analysis was applied to each variable. Results: The sample included 14,510 patients with a median age of 19.5 years. The number of patients and their ages demonstrated a clear seasonal variation, which peaked in the summer and winter. Increasing trends were observed for the proportion of male patients, use of non-extraction treatment modality, use of ceramic brackets, patients from provinces outside the Seoul region at large, patients transferred from private practitioners, and patients who underwent orthognathic surgery performed by university surgeons. Decreasing trends included the use of metal brackets and orthodontic treatment time. Conclusions: Time series analysis revealed a seasonal variation in some characteristics, and several variables showed changing trends over the past decade.

• Journal of the Korean earth science society
• /
• v.24 no.6
• /
• pp.578-591
• /
• 2003

To investigate the seasonal variation patterns of tidal flat sediments in semi-enclosed Hampyong and Kwangyang Bays, respectively west and south coasts of Korea, accumulation rate and grain-size in the sediments were monitored during 2${\sim}$4 years. The mud flats in the northern and eastern parts of Hampyong Bay were eroded in summer and deposited in winter, but mixed flats in the southern part of the bay show reversed seasonal variations to the mud flats. These variations are most likely connected with wave actions induced by monsoon and physiographic setting of the tidal flats in the bay. In contrast, the tidal flats of Kwangyang Bay were eroded in summer and deposited in other seasons except summer, different from the case of Hampyong Bay. The physiography of Kwangyang Bay are characterized by dominant flood tides and weak wave actions. However, in summer, the surface sediments were abruptly eroded by occasional typhoons and heavy rainfall. These weather conditions appear to be important factors to accelerate erosion on the tidal flat in semi-enclosed bays, south coast of Korea.

• Ocean and Polar Research
• /
• v.23 no.3
• /
• pp.245-253
• /
• 2001

To investigate the community structures and the their seasonal variation of phytoplankton and zooplankton, a study was conducted at 6 selected stations during the period from April 1999 to October 2000 in the marine ranching ground off Tongyeong. One hundred ninety species of phytoplankton were identified, including 146 diatoms, 38 dinoflagellates, 4 silicoflagellates and 2 euglenophytes. Phytoplankton standing crops varied extensively by months and stations, ranging from $3.0{\times}10^4\;cells/l\;to\;1.0{\times}10^6\;cells/l.$. The dominant species varied from the vertical distribution as well as seasonal changes. In April and July 1999, Skeletonema costatum and Ceratium fusus were predominant in both the surface and the bottom water columns. Leptocylindrus danicus was the dominant species in April and June 2000, and Thalassiosira spp. were also predominant in bottom waters in June 2000. Pseudonitzschia pungens and Chaetoceros spp. were the dominant species at both surface and near bottom waters in August and October 2000, respectively. Zooplankton abundance was comparatively high in April and July in 1999, and April, June, and October in 2000, but extremely low in November 1999. The density of dominant zooplankton was higher in 2000 than in 1999. Copepods were the most predominant group except for July 1999 when the bivalve larvae showed extremely high abundance. Acartia omorii and Oithona similis were the dominant or subdominant copepod species mainly in April 2000, and June/July, while O. davisae and O. plumifera had peaks in August and October 2000. Corycaeus affinis and Paracalanus sp. also showed higher peaks in April and June (or July), even though they occurred in all sampling time. Centropages abdominalis occurred abundantly only in April 1999. Oikopleura dioica, a gelatinous zooplankton, was another important zooplankton, showing high density in all samples except in July 1999.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.36 no.3
• /
• pp.298-305
• /
• 2003

Seasonal variation in species composition of fish in the estuary of Saemangeum water in the western coast of Korea was determined using seasonal samples collected by an otter trawl from April 2001 to February 2002. Species compositions did not differ significantly among the 4 stations (p>0.05, Wilcoxon signed-rank test). The cumulative number of species and species diversity (H') approached asymptote after four 30-min trawl hauls. Therefore 30-min trawl samples from each of the four stations were pooled to represent each season. A total of 45 species 2758 individuals and 30,346.8 g of fish were collected during the study period. Of the fish collected Leiognathus nuchalis, Synechogobius hasta, Neosalanx jordani, Konosirus punctatus and Chaeturichthys stigmatias predominated in abundance accounting for $68\%$ of the total number of individuals. Seasonal variation of fish abundance showed a similar trend to those of the other western coastal waters of Korea. The resident species were collected only in spring and autumn. Number of species and biomass were highest in summer due to the catch of many migrating species. In winter catch amount was low, and only 7 species were collected.. Brackish water fishes were more abundant in the study area, and Johnius grypotus and Cynoglossus joyneri were not premominated compared to the other coastal waters. This difference in species compositions may be related to the lower salinity in this estuarine habitat than in the other western coastal waters of Korea.

• The Journal of the Acoustical Society of Korea
• /
• v.21 no.3
• /
• pp.213-220
• /
• 2002

The sound wave in the sea propagates under the effect of water depth, sound velocity structure, sea surface and bottom roughness, and bottom sediment distribution. In particular the sound velocity structure in shallow water varies with time and space, an? the sediment distributes very variedly with place. In order to investigate the seasonal variation of low-frequency sound propagation in the Yellow Sea, the propagation experiments were conducted along the same track in the middle part of the Yellow Sea at various seasons of spring. summer, and autumn. In this paper we consider the measurement results on the propagation loss with the sound velocity structure, and investigate the seasonal variation of the propagation loss. As a result, the propagation losses measured in summer were larger than the losses in spring and autumn. And the propagation losses measured in autumn were smaller than the losses in spring. The seasonal change of the propagation loss increased with the rise of sound frequency and the propagation range.

• Ocean and Polar Research
• /
• v.28 no.3
• /
• pp.245-258
• /
• 2006

We investigated seasonal variations of the upper ocean temperature and the mixed layer depth (MLD) in an eddy-permitting global ocean general circulation model (OGCM) to assess the OGCM perfermance. The OGCM is based on the GFDL MOM3 which has a horizontal resolution of 0.5 degree and 30 vertical levels. The OGCM was integrated for 68 years using a monthly-mean climatological wind stress forcing. The model sea surface temperature (SST) and sea surface salinity were restored to the Levitus climatology with a time scale of 30 days. Annual-mean model SST shows a cold bias $(<\;-2^{\circ}C)$ in the summer hemisphere and a warm bias $(>\;1^{\circ}C)$ in the winter hemisphere mainly due to the restoring boundary condition of temperature. The model MLD captures well the observed features in most areas, with a slightly deep bias. However, in the Ross Sea and Weddell Sea, the model shows significantly deeper MLD than the climatology-mainly due to weak salinity stratifications in the model. For amplitude of seasonal variation, the model SST is smaller $(1{\sim}3^{\circ}C)$ than the observation largely due to the restoring surface boundary condition while the model MLD has larger seasonal variation $({\sim}50m)$. It is suggested that for more realistic simulation of the upper ocean structure in the present eddy-permitting ocean model, more refinements in the surface boundary condition for the thermohaline forcing and parameterization for vertical mixing are required, together with the incorporation of a sea-ice model.