289 research outputs found
Assessment of Agricultural Drought Considering the Hydrological Cycle and Crop Phenology in the Korean Peninsula
Hydrological changes attributable to global warming increase the severity and frequency of droughts, which in turn affect agriculture. Hence, we proposed the Standardized Agricultural Drought Index (SADI), which is a new drought index specialized for agriculture and crops, and evaluated current and expected droughts in the Korean Peninsula. The SADI applies crop phenology to the hydrological cycle, which is a basic element that assesses drought. The SADI of rice and maize was calculated using representative hydrological variables (precipitation, evapotranspiration, and runoff) of the crop growing season. In order to evaluate the effectiveness of SADI, the three-month Standardized Precipitation Index, which is a representative drought index, and rainfed crop yield were estimated together. The performance evaluation of SADI showed that the correlation between rainfed crop yield and SADI was very high compared with that of existing drought index. The results of the assessment of drought over the past three decades provided a good indication of a major drought period and differentiated the results for crops and regions. The results of two future scenarios showed common drought risks in the western plains of North Korea. Successfully validated SADIs could be effectively applied to agricultural drought assessments in light of future climate change, and would be a good example of the water-food nexus approach
Assessment of Agricultural Drought Considering the Hydrological Cycle and Crop Phenology in the Korean Peninsula
Hydrological changes attributable to global warming increase the severity and frequency of droughts, which in turn affect agriculture. Hence, we proposed the Standardized Agricultural Drought Index (SADI), which is a new drought index specialized for agriculture and crops, and evaluated current and expected droughts in the Korean Peninsula. The SADI applies crop phenology to the hydrological cycle, which is a basic element that assesses drought. The SADI of rice and maize was calculated using representative hydrological variables (precipitation, evapotranspiration, and runoff) of the crop growing season. In order to evaluate the effectiveness of SADI, the three-month Standardized Precipitation Index, which is a representative drought index, and rainfed crop yield were estimated together. The performance evaluation of SADI showed that the correlation between rainfed crop yield and SADI was very high compared with that of existing drought index. The results of the assessment of drought over the past three decades provided a good indication of a major drought period and differentiated the results for crops and regions. The results of two future scenarios showed common drought risks in the western plains of North Korea. Successfully validated SADIs could be effectively applied to agricultural drought assessments in light of future climate change, and would be a good example of the water-food nexus approach
Comb-rooted multi-channel synthesis of ultra-narrow optical frequencies of few Hz linewidth
We report a multi-channel optical frequency synthesizer developed to generate
extremely stable continuous wave lasers directly out of the optical comb of an
Er-doped fiber oscillator. Being stabilized to a high-finesse cavity with a
fractional frequency stability of at 0.1 s, the comb-rooted
synthesizer produces multiple optical frequencies of ultra-narrow linewidth of
1.0 Hz at 1 s concurrently with an output power of tens of mW per each channel.
Diode-based stimulated emission by injection locking is a key mechanism that
allows comb frequency modes to sprout up with sufficient power amplification
but no loss of original comb frequency stability. Channel frequencies are
individually selectable with a 0.1 GHz increment over the entire comb bandwidth
spanning 4.25 THz around a 1550 nm center wavelength. A series of out-of-loop
test results is discussed to demonstrate that the synthesizer is able to
provide stable optical frequencies with the potential for advancing diverse
ultra-precision applications such as optical clocks comparison, atomic line
spectroscopy, photonic microwaves generation, and coherent optical
telecommunications.Comment: 19 pages, 4 figure
A Case of Central Retinal Artery Occlusion after Chiropractic Manipulation of the Neck
Here we report a case of central retinal artery occlusion after chiropractic manipulation on the neck. A 49-year old man presented at the hospital because of sudden visual loss in his right eye after chiropractic neck manipulation. He had received chiropractic manipulation of the neck by a chiropractor eight days prior. When he first visited us, his best corrected visual acuity in his right eye was hand motion. A full ophthalmic examination was performed. There was cherry-red spot in the macula in his right eye. We performed a fluorescein angiogram and cervical color Doppler. The arterio-venous transit time in the fluorescein angiogram was delayed, and we detected stenosis of the right internal carotid artery with diffuse atherosclerotic plaques in the right common carotid artery. We prescribed ginko biloba extract (Tanamin). Three years after his first visit, the best corrected visual acuity of his right eye was 20 / 200
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