Climate change due to global warming causes a rise in atmospheric air temperature to rise and extreme shift in precipitation patterns. Carbon dioxide (CO2) is widely known as one of the major cause of global warming and accounts for about 72% of total greenhouse gas emissions. Agriculture is more vulnerable to climate change than other industries. Many studies have been conducted to investigate how agroecosystems, both natural and controlled, will respond to the rising level of CO2. Studies on the responses of crops and agricultural environments to climate change are crucial in predicting changes in agro-ecosystems. Research facilities for various types of CO2 treatment have been developed. The representative research facilities are SAR (Soil-Plant-Atmosphere-Research), OTC (Open Top Chamber), FACE (Free Air CO2 Enrichment System), and TGC & CTGC (Temperature Gradient Chamber & CO2-Temperature Gradient Chamber). Therefore, this study reviewed research data and their application in agriculture.

2019년 1월부터 11월까지 서울약령시장에서 유통되는 식·약 공용 농산물 총 187건을 대상으로 곰팡이독소 동시 다성분 SPE 컬럼으로 정제 후 LC-MS/MS로 분석하여 곰팡이독소 8종의 동시분석법 유효성을 검증하고, 확립된 분석법으로 곰팡이독소 오염도 파악 및 위해평가를 실시하였다. LC-MS/MS를 이용한 동시분석법의 유효성 검증은 매질효과, 직선성, 검출한계, 정량한계, 정확성 및 정밀성으로 하였다. 매질 보정 검량선의 상관계수(r2)는 0.9999이상의 우수한 직선성을 보였고, 검출한계는 0.02-0.11 μg/ kg였고, 정량한계는 0.06-0.26 μg/kg였고, 회수율은 81.2- 118.7%였고, 상대표준편차는 0.33-8.90%로 우수한 재현성을 나타냈다. 확립된 분석법으로 검사한 결과 기준이 설정된 아플라톡신은 B1이 1.18-7.29 μg/kg (기준: 총 아플라톡신 15.0 μg/kg이하, B1 10.0 μg/kg이하)으로 기준 이내로 검출되었고, 아플라톡신 B2, G1 및 G2는 검출되지 않았다. 기준이 미설정된 곰팡이독소는 푸모니신(0.84-14.25 μg/ kg) 오크라톡신 A (0.76-17.42 μg/kg) 및 제랄레논(1.73- 15.96 μg/kg)이 검출되었다. 위해평가 결과 아플라톡신 B1의 1일 인체노출량은 0.00052 μg/kg b.w./day였고, 푸모니신 및 제랄레논의 일일섭취한계량 대비 각각 0.04%, 0.24% 였고, 오크라톡신 A의 주간섭취한계량 대비 4.76%로 우리나라 국민들이 식·약 공용 농산물 섭취로 인한 곰팡이 독소 위해도는 안전한 것으로 평가되었다.

농경지는 농업부문에서 발생하는 온실가스인 N2O의 배출원이다. 따라서 농경지에서 N2O를 줄일 수 연구가 필요하며, 본 연구에서는 농경지에 작물재배 시 무경운기술을 적용하고, 녹비작물로서 호밀과 헤어리배치를 각각 투입하여 N2O 배출량 비교 평가하였다. 재배 기간 중 토양에 질소원이 공급된 초기에 배출량이 높았으며, 토양온도는 20~25°C, 수분함량은 20~30% 범위에서 N2O 배출량이 높았다. 작물재배기간 동안 경운 유무와 투입된 질소원에 따른 처리구간 통계적 유의한 차이가 발생했다. 농경지 토양에서 배출되는 N2O는 무경운을 통해 CF, HV 그리고 RY 처리구에서 각각 51.8%, 31.7% 그리고 59.6% 감축되었다. 또한 무경운 헤어리배치 (HV-NT) 처리구에서 관행 (CFCT) 처리구 대비 59.0% N2O 배출을 저감할 수 있었다. 헤어리배치를 투입함으로써 화학비료 사용량을 줄일 수 있고, 무경운을 통해 토양 교란을 방지하여 농경지 토양에서 배출되는 N2O를 저감할 수 있었다. 이러한 감축기술에 대한 온실가스 저감효과를 평가하는 연구와 향후 온실가스 감축사업과 연계할 수 있도록 검인증 방법을 포함한 방법론 구축 등이 필요하다. 이후 농업분야 온실가스 감축사업인 배출권거래제 외부사업, 농업농촌 자발적 온실가스 감축사업, 저탄소농축산물 인증제 등과 연계하여 농업현장에서 활용할 수 있도록 해야 한다.

작물 재배시에 질소비료와 유기물인 헤어리베치 그리고 LCU효과지연성 복합비료 등 질소공급원별로 토양에 시용하여 N2O 배출에 영향을 주는 요인들의 특성을 조사하였다. 그리고 그 요인들이 N2O 배출에 얼마나 영향을 주는지를 정량적으로 밝히고 온실가스 배출의 영향 인자들에 대해 온실가스 감축 효과를 종합적으로 평가하였다. N2O 배출에 영향을 미치는 요인은 토양온도, 토양수분과 무기태질소 등이다. 이 세 가지 요인 중 N2O 배출에 가장 크게 영향을 미치는 요인은 무기태질소 (콩 65.5%, 51.2%)>토양수분함량 (콩 19.2%, 고추 28.8%)>토양온도 (콩 15.2%, 고추 22.0%) 순으로 나타났다. 수량과 비료이용효율은 LCU 효과지연성 복합비료 처리에서 가장 높았다. N2O 배출량은 LCU효과지연성 복합비료와 NPK+헤어리베치 처리에서 차이를 보이지 않아 종합적인 결과는 수량과 비료이용효율 그리고 낮은 N2O 배출량을 보인 LCU효과지연성 복합비료 처리가 가장 양호한 것으로 나타났다. 따라서 앞으로 N2O 배출을 저감할 수 있는 토양 양분관리 기술 개발 연구가 확대되면 온실가스 배출저감 대책에 도움이 될 것으로 기대할 수 있다.

Importance of climate change and its impact on agriculture and environment has increased with the rise in the levels of Green House Gases (GHGs) in the atmosphere. To slow down the speed of climate change, numerous efforts have been applied in industrial sectors to reduce GHGs emission and to enhance carbon storage. In the agricultural sector, several types of research have been performed with emphasis on GHGs emission reduction; however, only a few work has been done in understanding the role of carbon sink on reduction in GHGs emission. In this study, we investigated ecosystem carbon balance and soil carbon storage in an agricultural paddy field. The results obtained were as follows: 1) Evaluation of soil C sequestration in paddy field was average 3.88 Mg CO2 ha-1 following NPK+rice straw compost treatment, average 3.22 Mg C ha-1 following NPK+hairy vetch treatment, and average 1.97 Mg CO2 ha-1 following NPK treatment; and 2) Net ecosystem production (NEP) during the paddy growing season was average 14.01 Mg C ha-1 following NPK+hairy vetch treatment, average 12.60 Mg CO2 ha-1 following NPK+rice straw compost treatment, and average 11.31 Mg CO2 ha-1 following NPK treatment. Therefore, it is proposed that organic matter treatment can lead to an increase in soil organic carbon accumulation and carbon sock of crop ecosystem in fields compared to chemical fertilizers.

The Korean Institute of Technology Satellite (KITSAT-1) is the first satellite developed by the Satellite Technology Research Center and the University of Surrey. KITSAT-1 is orbiting the Earth’s orbit as space debris with a 1,320 km altitude after the planned mission. Due to its relatively small size and altitude, tracking the KITSAT-1 was a difficult task. In this research, we analyzed the tracking results of KITSAT-1 for one year using the Midland Space Radar (MSR) in Texas and the Poker Flat Incoherent Scatter Radar (PFISR) in Alaska operated by LeoLabs, Inc. The tracking results were analyzed on a weekly basis for MSR and PFISR. The observation was conducted by using both stations at an average frequency of 10 times per week. The overall corrected range measurements for MSR and PFISR by LeoLabs were under 50 m and 25 m, respectively. The ionospheric delay, the dominant error source, was confirmed with the International Reference of Ionosphere-16 model and Global Navigation Satellite System data. The weekly basis orbit determination results were compared with two-line element data. The comparison results were used to confirm the orbital consistency of the estimated orbits.

The Optical Wide-field patroL-Network (OWL-Net) is a global optical network for Space Situational Awareness in Korea. The primary operational goal of the OWL-Net is to track Low Earth Orbit (LEO) satellites operated by Korea and to monitor the Geostationary Earth Orbit (GEO) region near the Korean peninsula. To obtain dense measurements on LEO tracking, the chopper system was adopted in the OWL-Net’s back-end system. Dozens of angle-only measurements can be obtained for a single shot with the observation mode for LEO tracking. In previous work, the reduction process of the LEO tracking data was presented, along with the mechanical specification of the back-end system of the OWL-Net. In this research, we describe an integrity assessment method of time-position matching and verification of results from real observations of LEO satellites. The change rate of the angle of each streak in the shot was checked to assess the results of the matching process. The time error due to the chopper rotation motion was corrected after re-matching of time and position. The corrected measurements were compared with the simulated observation data, which were taken from the Consolidated Prediction File from the International Laser Ranging Service. The comparison results are presented in the In-track and Cross-track frame.

Studies looking at many aspects of SNS addiction have dramatically increased in recent years. Most of the SNS addiction research has focused on individual behaviors. There is little academic research about SNS addiction in the workplace. This study, therefore, plans to examine the organizational behaviors related to SNS addiction in the workplace. We investigate whether negative behaviors in the workplace induce SNS addiction, and how SNS addiction influences the organizational or social attitudes of employees. We also explore the possible mediating effect of SNS addiction. We use an online survey and collected 285 responses from office workers in South Korea. The results tested by a structural equation modeling indicate, first, that both abusive supervision and workplace bullying have aroused SNS addiction among employees; second, employees’ SNS addiction increases both from work-to-family-conflicts and family-to-work-conflicts; and third, SNS addiction fully mediates the relationship between abusive supervision and workplace bullying, as well as the relationship among abusive supervision, workplace bullying, and work-family conflicts. The study finds that abusive supervision and workplace bullying are important antecedents of SNS addiction, and that SNS addiction affects conflicts in both work-to-family and family-to-work situations. Therefore, companies should be cognizant of potential mediating influences in monitoring employees’ SNS usage in order to improve their work environments.

Radar sensors are used for space situational awareness (SSA) to determine collision risk and detect re-entry of space objects. The capability of SSA radar system includes radar sensitivity such as the detectable radar cross-section as a function of range and tracking capability to indicate tracking time and measurement errors. The time duration of the target staying in a range cell is short; therefore, the signal-to-noise ratio cannot be improved through the pulse integration method used in pulse-Doppler signal processing. In this study, a method of improving the signal-to-noise ratio during range migration is presented. The improved detection performance from signal processing gains realized in this study can be used as a basis for comprehensively designing an SSA radar system.

With increased human activity in space, the risk of re-entry and collision between space objects is constantly increasing. Hence, the need for space situational awareness (SSA) programs has been acknowledged by many experienced space agencies. Optical and radar sensors, which enable the surveillance and tracking of space objects, are the most important technical components of SSA systems. In particular, combinations of radar systems and optical sensor networks play an outstanding role in SSA programs. At present, Korea operates the optical wide field patrol network (OWL-Net), the only optical system for tracking space objects. However, due to their dependence on weather conditions and observation time, it is not reasonable to use optical systems alone for SSA initiatives, as they have limited operational availability. Therefore, the strategies for developing radar systems should be considered for an efficient SSA system using currently available technology. The purpose of this paper is to analyze the performance of a radar system in detecting and tracking space objects. With the radar system investigated, the minimum sensitivity is defined as detection of a 1-m2 radar cross section (RCS) at an altitude of 2,000 km, with operating frequencies in the L, S, C, X or Ku-band. The results of power budget analysis showed that the maximum detection range of 2,000 km, which includes the low earth orbit (LEO) environment, can be achieved with a transmission power of 900 kW, transmit and receive antenna gains of 40 dB and 43 dB, respectively, a pulse width of 2 ms, and a signal processing gain of 13.3 dB, at a frequency of 1.3 GHz. We defined the key parameters of the radar following a performance analysis of the system. This research can thus provide guidelines for the conceptual design of radar systems for national SSA initiatives.

The key risk analysis technologies for the re-entry of space objects into Earth’s atmosphere are divided into four categories: cataloguing and databases of the re-entry of space objects, lifetime and re-entry trajectory predictions, break-up models after re-entry and multiple debris distribution predictions, and ground impact probability models. In this study, we focused on reentry prediction, including orbital lifetime assessments, for space situational awareness systems. Re-entry predictions are very difficult and are affected by various sources of uncertainty. In particular, during uncontrolled re-entry, large spacecraft may break into several pieces of debris, and the surviving fragments can be a significant hazard for persons and properties on the ground. In recent years, specific methods and procedures have been developed to provide clear information for predicting and analyzing the re-entry of space objects and for ground-risk assessments. Representative tools include object reentry survival analysis tool (ORSAT) and debris assessment software (DAS) developed by National Aeronautics and Space Administration (NASA), spacecraft atmospheric re-entry and aerothermal break-up (SCARAB) and debris risk assessment and mitigation analysis (DRAMA) developed by European Space Agency (ESA), and semi-analytic tool for end of life analysis (STELA) developed by Centre National d’Etudes Spatiales (CNES). In this study, various surveys of existing re-entry space objects are reviewed, and an efficient re-entry prediction technique is suggested based on STELA, the life-cycle analysis tool for satellites, and DRAMA, a re-entry analysis tool. To verify the proposed method, the re-entry of the Tiangong-1 Space Lab, which is expected to re-enter Earth’s atmosphere shortly, was simulated. Eventually, these results will provide a basis for space situational awareness risk analyses of the re-entry of space objects.

The optical wide-field patrol network (OWL-Net) is a Korean optical surveillance system that tracks and monitors domestic satellites. In this study, a batch least squares algorithm was developed for optical measurements and verified by Monte Carlo simulation and covariance analysis. Potential error sources of OWL-Net, such as noise, bias, and clock errors, were analyzed. There is a linear relation between the estimation accuracy and the noise level, and the accuracy significantly depends on the declination bias. In addition, the time-tagging error significantly degrades the observation accuracy, while the time-synchronization offset corresponds to the orbital motion. The Cartesian state vector and measurement bias were determined using the OWL-Net tracking data of the KOMPSAT-1 and Cryosat-2 satellites. The comparison with known orbital information based on two-line elements (TLE) and the consolidated prediction format (CPF) shows that the orbit determination accuracy is similar to that of TLE. Furthermore, the precision and accuracy of OWL-Net observation data were determined to be tens of arcsec and sub-degree level, respectively.

This research was carried out to identify aerodynamic property as a function of moisture content for designing equipment such as for post-harvest management. Terminal velocity of two wheat varieties {Backjjung (B) and Jogyeong (J)} with selected sound, damaged kernel and foreign materials (Wheat stick, Wheat husks) were measured with a designed vertical wind column at different moisture contents from about 9 to 30% wet basis. The results showed that terminal velocity of wheat and foreign materials except of Jogyeong’s husks (p<0.05) had a significant difference at p<0.001. With increasing moisture content, the aerodynamic property values of the kernels and foreign materials of the two wheat varieties increased linearly. In detail, terminal velocity of sound and damaged kernel increased from 5.46 to 7.13 m/sec (B) and 7.48 to 8.60 m/sec (J), damaged kernel from 5.91 to 7.00 m/sec (B) and 6.48 to 7.75 m/sec (J). For foreign materials the terminal velocity of wheat stick increased from 2.92 to 4.07 m/sec (B) and 3.74 to 5.22 m/sec (J) whereas that of husks from 1.07 to 1.85 m/sec (B) and 2.02 to 2.33 m/sec (J) each. For air separation of wheat and foreign materials, the air flow should be less than 5.22 m/sec due to the range (1.07~5.22 m/sec) of foreign materials in wheat.

As described in the previous paper (Park et al. 2013), the detector subsystem of optical wide-field patrol (OWL) provides many observational data points of a single artificial satellite or space debris in the form of small streaks, using a chopper system and a time tagger. The position and the corresponding time data are matched assuming that the length of a streak on the CCD frame is proportional to the time duration of the exposure during which the chopper blades do not obscure the CCD window. In the previous study, however, the length was measured using the diagonal of the rectangle of the image area containing the streak; the results were quite ambiguous and inaccurate, allowing possible matching error of positions and time data. Furthermore, because only one (position, time) data point is created from one streak, the efficiency of the observation decreases. To define the length of a streak correctly, it is important to locate the endpoints of a streak. In this paper, a method using a differential convolution mask pattern is tested. This method can be used to obtain the positions where the pixel values are changed sharply. These endpoints can be regarded as directly detected positional data, and the number of data points is doubled by this result.

The correlation between meteorological data collected at the optical wide-field patrol network (OWL-Net) Station No. 1 and the seeing of satellite optical observation data was analyzed. Meteorological data and satellite optical observation data from June 2014 to November 2015 were analyzed. The analyzed meteorological data were the outdoor air temperature, relative humidity, wind speed, and cloud index data, and the analyzed satellite optical observation data were the seeing full-width at half-maximum (FWHM) data. The annual meteorological pattern for Mongolia was analyzed by collecting meteorological data over four seasons, with data collection beginning after the installation and initial set-up of the OWL-Net Station No. 1 in Mongolia. A comparison of the meteorological data and the seeing of the satellite optical observation data showed that the seeing degrades as the wind strength increases and as the cloud cover decreases. This finding is explained by the bias effect, which is caused by the fact that the number of images taken on the less cloudy days was relatively small. The seeing FWHM showed no clear correlation with either temperature or relative humidity.

Inactive space objects are usually rotating and tumbling as a result of internal or external forces. KOREASAT 1 has been inactive since 2005, and its drift trajectory has been monitored with the optical wide-field patrol network (OWL-Net). However, a quantitative analysis of KOREASAT 1 in regard to the attitude evolution has never been performed. Here, two optical tracking systems were used to acquire raw measurements to analyze the rotation period of two inactive satellites. During the optical campaign in 2013, KOREASAT 1 was observed by a 0.6 m class optical telescope operated by the Korea Astronomy and Space Science Institute (KASI). The rotation period of KOREASAT 1 was analyzed with the light curves from the photometry results. The rotation periods of the low Earth orbit (LEO) satellite ASTRO-H after break-up were detected by OWL-Net on April 7, 2016. We analyzed the magnitude variation of each satellite by differential photometry and made comparisons with the star catalog. The illumination effect caused by the phase angle between the Sun and the target satellite was corrected with the system tool kit (STK) and two line element (TLE) technique. Finally, we determined the rotation period of two inactive satellites on LEO and geostationary Earth orbit (GEO) with light curves from the photometry. The main rotation periods were determined to be 5.2 sec for ASTRO-H and 74 sec for KOREASAT 1.

본 연구는 국내원맥 중 백중밀 및 조경밀의 함수율 9~30%(w.b.) 범위내에서의 물리적 특징 중 산물밀도, 동안 식각, 비중, 천립중, 장축길이, 단축길이, 두께 및 면적을 분석하여 함수율간의 상관관계를 구명함으로써 국내밀의 체계적인 수확 후 관리 중 정선, 선별, 이송, 저장 및 가공 공정에서의 설계공정 및 기초자료로 활용하고자 연구하였 다. 함수율 9~30%(w.b.) 범위내에서의 백중 및 조경밀의 산물밀도는 함수율이 증가할수록 서서히 감소하였으며, 백 중밀은 754 kg/m3에서 664 kg/m3로 감소하였고, 조경밀은 776.1 kg/m3에서 660.0 kg/m3로 감소하였다. 비중 또한 함수 율이 증가할수록 서서히 감소하였으며, 백중밀의 경우 1.2950에서 1.2265로 조경밀은 1.3379에서 1.2671로 측정되 었다. 반면에 천립중 및 동안식각은 함수율이 증가할수록 점차 증가하였으며, 동안식각은 함수율 20%(w.b.)이상부 터는 거의 변화가 없었다. 천립중은 백중밀보다 조경밀이 크게 측정되었으며 그 값은 32.26~41.51 g(백중밀) 및 45.30~63.07 g(조경밀)로 조경밀이 현저히 크게 측정되었 다. 함수율에 따른 장축길이, 단축길이, 두께 및 면적은 함수 율이 증가할수록 점차 증가하였다. 백중밀의 장축길이는 6.42 mm에서 7.20 mm로 조경밀은 8.71 mm에서 9.15 mm로 증가하였고, 단축길이 역시 2.90~3.49 mm(백중밀) 및 4.12~4.43 mm(조경밀)으로 증가하였으며, 두께 2.94~3.20 mm(백중밀) 및 3.29~3.63 mm(조경밀), 면적은 14.13~19.44 mm2(백중밀), 27.75~31.25 mm2(조경밀)로 각각 측정되었 다. 이로써 함수율에 따른 우리밀의 물리적 특징이 구명되 었으며, 이는 우리밀에 적합한 건조저장시설 및 수확 후 관리모델 개발에 도움이 될 것으로 판단된다.

The Accurate Ranging System for Geodetic Observation – Mobile (ARGO-M) was successfully developed as the first Korean mobile Satellite Laser Ranging (SLR) system in 2012, and has joined in the International Laser Ranging Service (ILRS) tracking network, DAEdeoK (DAEK) station. The DAEK SLR station was approved as a validated station in April 2014, through the ILRS station “data validation” process. The ARGO-M system is designed to enable 2 kHz laser ranging with millimeter-level precision for geodetic, remote sensing, navigation, and experimental satellites equipped with Laser Retro-reflector Arrays (LRAs). In this paper, we present the design and development of a next generation high-repetition-rate SLR system for ARGO-M. The laser ranging rate up to 10 kHz is becoming an important issue in the SLR community to improve ranging precision. To implement high-repetition-rate SLR system, the High-repetition-rate SLR operation system (HSLR-10) was designed and developed using ARGO-M Range Gate Generator (A-RGG), so as to enable laser ranging from 50 Hz to 10 kHz. HSLR-10 includes both hardware controlling software and data post-processing software. This paper shows the design and development of key technologies of high-repetition-rate SLR system. The developed system was tested successfully at DAEK station and then moved to Sejong station, a new Korean SLR station, on July 1, 2015. HSLR-10 will begin normal operations at Sejong station in the near future.

The first Korean satellite laser ranging (SLR) system, Daedeok SLR station (DAEK station) was developed by Korea Astronomy and Space Science Institute (KASI) in 2012, whose main objectives are space geodesy researches. In consequence, Korea became the 25th country that operates SLR system supplementing the international laser tracking network. The DAEK station is designed to be capable of 2 kHz laser ranging with precision of a few mm both in daytime and nighttime observation of satellites with laser retro-reflector array (LRA) up to the altitude of 25,000 km. In this study, characteristics and specifications of DAEK station are investigated and its data quality is evaluated and compared with International Laser Ranging Service (ILRS) stations in terms of single-shot ranging precision. The analysis results demonstrated that the DAEK station shows good ranging performance to a few mm precision. Currently, the DAEK station is under normal operations at KASI headquarters, however, it will be moved to Sejong city in 2014 to function as a fundamental station for space geodesy researches in combination with other space geodesy systems (GNSS, VLBI, DORIS, etc.).