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Veterinary antibiotics (VAs) administered to livestock are introduced into the soil through livestock manure and compost. These antibiotics can run off to surface water or leach into groundwater during rainfall, causing problems such as antibiotic contamination or the occurrence of antibiotic-resistant bacteria. In this study, an analytical method for detecting four classes of VAs (penicillin, tetracyclines, macrolides, and sulfonamides) in river water and soil was developed, and the occurrence of residual antibiotics in the agricultural environment was monitored. Soil samples were extracted with the McIlvain buffer solution and pretreatment was conducted using solid-phase extraction, followed by liquid chromatography-tandem mass spectrometry to quantify target VAs. The results of this study showed that the recovery ranged from 62 to 121% in river water and 40.2–149.3% in soil. Among the other VAs, amoxicillin and spiramycin were observed to have low recoveries in all the samples. The method detection limit (MDL) was calculated in the range of 2.1–12.3 ng L−1 in river water and 1.2–13.2 ng kg−1 in soil, and the limit of quantification was 6.6–39.2 ng L−1 and 4.0–42.0 ng kg−1, respectively. This optimal method was then applied to measure the residual concentrations of VAs in river water, sediment, and soil samples around the Muhan watershed in Korea. A total of seven antibiotics were detected, and their concentrations ranged from 0.014 to 0.309 μg L−1in river water, and 1.45–9.04 μg kg−1 in sediment and arable soil. This method can be used to screen VAs in river water and soil and is expected to be used as primary data for examining the occurrence and fate of antibiotics in agricultural environments.

In this study, the comprehensive study of the performance investigation of Solid Desiccant Based Dehumidification (SDBD) system which involves the desiccant selection and desiccant coating with metallic heat exchanger was conducted at the mild humid conditions which represent the humid air conditions in summer, South Korea. The water uptake capacity of three different solid desiccants was investigated to find the proper solid desiccant in the SDBD system under the given operating conditions. Among the three different solid desiccants, the aluminum fumarate based metal organic frameworks (MOFs) was selected as the best solid desiccant for SDBD system and it has the maximum water uptake capacity around 0.398 g·g−1 for given operating conditions. The aluminum fumarate based metal organic frame works (MOFs) was coated on the metallic surface of heat exchanger by current developed coating method and the desiccant and binder solution is consistent of 10% of binder and solvent mixture and 90% of aluminum fumarate based MOFs. As a result, the increase of coating thickness from 0.05 mm to 0.2 mm and operating time from 150 s to 300 s can achieve the 113% and 131% of dehumidification performance enhancement in average, respectively. Remarkably, over 160% improvement of dehumidification performance in average can be achieved by the decrease of space velocity from 13 s−1 to 5.2 s−1.

BACKGROUND: The concern over heavy metal(loid)s in arable land and agricultural products increases for public health in recent years. This study aims to identify transition characteristics of heavy metal(loid)s and to assess dietary risk in barley grown at the major producing districts in Korea. METHODS AND RESULTS: The soil and barley samples were collected from 38 locations around the major producing districts at Jeollabuk-do in Korea for the propose of examining the concentrations of heavy metal(loid)s. The 34 barley samples were separately purchased on the market for the same survey. The average concentration and range of arsenic (As), cadmium (Cd) and lead (Pb) in barley grown at the major producing districts in Korea were 0.037 (0.016-0.094), 0.028 (0.004-0.083) and 0.137 (0.107-0.212) mg kg-1, respectively. Currently, the maximum allowable level for barley Pb is set at 0.2 mg kg-1 in Korea, and the monitoring results suggested that some samples exceeded the maximum allowable level and required appropriate farming management. Bio-concentration factor values by heavy metal( loid)s in barley were high at Cd, copper (Cu) and zinc (Zn), similar to other crops, while As and Pb were low, indicating low transferability. CONCLUSION: Human exposure to As, Cd and Pb through dietary intake of barley might not cause adverse health effects due to relatively low concentrations, although the Pb in some barley was detected higher than the maximum allowable level. Further study on uptake and accumulation mechanism of Pb by barley might be required to assess the human health risk associated with soil contamination.

Most previous studies on adsorption chillers were conducted using the same adsorption and desorption times. Instead, this study analyzed various adsorption/desorption time allocations, and systematically examined the effect of cycle time allocation on system performance. The results provide physical insights for 3-bed adsorption chillers. The effect of hot water temperature and cycle time on the optimum adsorption/desorption time ratio was also examined. Setting the proper adsorption and desorption times was much more important for smaller cycle times. The highest degradation in COP (coefficient of performance) found was 36% at 300 s of cycle time, compared with the conventional 1:1 ratio. When the temperature of the heat source is low, the ratio of adsorption/desorption time was not significantly affected, however, for higher performance at high temperature, a longer adsorption time than desorption time was required.

Air pollution has increasingly been recognized as a major healthcare concern. Air pollution, particularly fine particulate matter (≤ 2.5 μm in aerodynamic diameter [PM2.5]) has demonstrated an increase in adverse cardiovascular events. This study aimed to assess the cardiovascular response to personal exposure to different levels of PM2.5. This prospective cohort study enrolled healthy volunteers aged ≥ 18 years with no cardiovascular disease. Study subjects carried personal exposure monitor of PM2.5, digital thermo-hygrometer for temperature and humidity, 24-h blood pressure monitor, and continuous electrocardiogram monitor. Measurements were repeated twice with an interval of 6–12 months. Statistical models consisted of generalized estimation equations to various repeated measures of each subject. A total of 22 subjects were enrolled in this study between July 2018 and January 2019. Measurement was performed twice in all participants, and a total of 36 data were collected except for insufficient data collection. The mean age of the study population was 41.6 years, and 95% of the subjects were females. No study subjects had hypertension or other cardiovascular diseases. The average systolic blood pressure increased with higher PM2.5 levels with marginal significance (0.22 mmHg [95% confidential intervals − 0.04 to 0.48 mmHg] per 10 μg/m3 of PM2.5). All parameters for heart rate variability significantly decreased with a higher level of PM2.5. In this study, we measured individual personal exposure to PM2.5 by using a portable device. We found that 24-h exposure to high levels of PM2.5 was associated with a significant decrease in heart rate variability, suggesting impaired autonomous nervous function.

Veterinary antibiotics (VAs) released into the environment are a concern because of the possibility for increasing antibiotic-resistance genes. The concentrations of six VAs, chlortetracycline, oxytetracycline, tetracycline, sulfamethazine, sulfamethoxazole, and sulfathiazole, in manure-based compost, soil, and crops were measured using liquid chromatography–tandem mass spectrometry. Mass balance analysis was conducted based on the measured antibiotic concentration, cultivation area, and amount of manure-based compost applied. The result showed that the detected mean concentration of VAs ranges was 3.52~234.19 μg/kg, 0.52~13.08 μg/kg, and 1.05~39.57 μg/kg in manure-based compost, soil, and crops, respectively, and the substance of VAs detected in different media was also varied. Mass balance analysis showed that the VAs released from the manure-based compost can remain in soil (at rates of 26% to 100%), be taken up by crops (at rates of 0.4% to 3.7%), or dissipated (at rates of 9% to 73%) during the cultivation period. Among the six VAs, chlortetracycline and oxytetracycline mainly remained in the soil, whereas sulfamethoxazole and sulfathiazole were mainly dissipated. Although we did not verify the exact mechanism of the fate and distribution of VAs in this study, our results showed that these can vary depending on the different characteristics of VAs and the soil properties.

An adsorption chiller is a highly promising cooling technology, but it has not been widespread because there are many uncertainties to solve the complex thermal and mass transfer phenomena. An adsorption chiller is composed of multi-modules and the tube inlet temperature decreases (or increases) during the adsorption process (or desorption process) from module to module in serially connected modules. It has been reported that the optimal fin height depends on the tube inlet temperature, thus using a different fin height for each module should potentially enhance the overall system performance of the adsorption chiller. Till now, there have been few studies which evaluated adsorption chiller performance from a system viewpoint. Most only considered a single fin space. Thus, no study has considered improving total system performance by using different conditions for different modules in series. We conducted a numerical study of 5 modules in series, using different fin heights. The coefficient of performance (COP) and specific cooling power (SCP) of modules with stepwise-linearly decreasing fin height were compared with those of modules with constant fin height. An 8.5% increase in COP and a 9.56% increase in SCP were observed. This enhancement will be much larger if more than five modules are connected to match the cooling capacity. The decrease (or increase) in tube inlet temperature accumulated in the series of modules. The last module, the 5th showed the most significant enhancement in COP and SCP, of 27.9% and 38.4%, respectively.

한약재의 불법 유통을 방지하기 위해 신속 정확한 원산지 판별방법 개발이 필요함에 따라 TDU-GC/MS를 이용하여 한국품종당귀와 외국품종 당귀를 판별함과 동시에 한국품종 당귀의 재배지가 한국인지를 판별할 수 있는 기법을 연구하였다. 당귀추출물을 열탈착 시킨 후 냉각응축시스템에서 응축시켜 일시에 GC/MS로 분석한 결과 국산 품종 당귀(참당귀)는 TIC의 RT 26.9-27.2에서 coumarin 유도체인 decursin과 decursinol peak가 확인되었다. 중국 품종 당귀(중당귀)의 경우 RT 17.2 부근에서 ligustilide의 peak가 검출되었다. 국산 품종 참당귀 원산지에 따른 휘발성분의 차이를 알아보기 위하여 twister로 흡착하여 TDU-GC/MS로 m/z 40-400 amu 범위에서 mass spectrum을 측정하였다. 참당귀의 국내 및 중국 재배 시료 TIC는 전반적으로 같은 경향을 냈으나 TIC를 부분 scan한 결과 RT 15.4-16.1에서 국내 및 중국 재배의 peak pattern 차이를 확인할 수 있었다. Peak A (RT 15.54)과 B (RT 16.05)의 비율은 국내 재배는 0.0-0.2, 중국 재배의 경우 0.5-2.8으로서 TDU-GC/MS의 TIC peak pattern 비교를 통한 원산지 판별 가능성을 확인하였다.

Mortality difference by age, sex, body mass index (BMI) in gastric cancer (GC) has been controversial. We evaluated sex-specific mortality by age and BMI. A total of 5961 patients diagnosed with GC from 2005 to 2013 in a single tertiary center were included and were followed until December 2017. The plot in goodness-of-fit-test by sex was crossed, so we performed sex-specific analysis. Overall mortality was lower in women than in men (adjusted hazard ratio [aHR], 0.72). Favor outcomes in women compared to men were observed among patients older than 60 yr (aHR, 0.64; 95% CI, 0.56–0.74), a BMI less than 25 kg/m2 (aHR, 0.69; 95% CI, 0.61–0.79), and stage I (aHR, 0.46; 95% CI, 0.38–0.56). In sex-specific analysis, mortality increased in age older than 60 yr in men, whereas it increased in both extreme ages (

Atrial fibrillation is a common cardiac arrhythmia and an important risk factor for stroke and cardiovascular morbidity. However, there is limited evidence regarding the association of air pollution with atrial fibrillation. This study aimed to compare the short-term and long-term effects of air pollution on atrial fibrillation.A nationwide cohort from the Korean general population.Different analytical approaches were used for short-term and long-term effects. For the analysis of short-term effects, the daily incidence of emergency admissions for atrial fibrillation was identified. The relationship of atrial fibrillation with air pollutants, including PMDuring the study period, 1137 emergency visits were identified in Seoul as being associated with atrial fibrillation. A 10-μg/mThis study suggests that short-term exposure to PM

To overcome the problem of peak electricity demand caused by the use of air-conditioning in the summer, researchers have been focusing their interest on adsorption chillers, which are an environmentally friendly technology in that they use waste heat as their power source and water as a refrigerant. In the present study, to improve the performance of an adsorption chiller, FAPO4-5 adsorbents were synthesized using two hydrothermal synthetic methods, and then characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), N2 adsorption/desorption isotherms and water adsorption isotherms. Coatings of the adsorbent were applied to an aluminum substrate. Six different coating solutions were used, with a 5.0 wt%, 10.0 wt%, and 15.0 wt% content of epoxy-based and silicone-based binders, respectively. The surface features of adsorbent coating were observed with scanning electron microscopy (SEM). To determine the variation in the water adsorption properties of the adsorbents according to the binder type, each adsorbent was subjected to water adsorption isotherm analysis at 25 °C. The coating thickness was calculated by three dimension coordinate measuring machine. Cross-cut tests (performed according to ISO 2409:2013) were carried out to assess the strength of the adhesion of the coating to the aluminum substrate.

Absorption heat transformer (AHT) has played a role in producing available heat from the low temperature of waste heat sources. This study proposes two operating modes regarding the way to supply heat source to the AHT system, and aims to investigate the operating characteristics of the steam generating AHT system concerning heating source temperature. First, this study describes the thermodynamic cycle of the single stage AHT operating with water-lithium bromide pair, and two operating modes are illuminated: a forward flow mode for heat source input to the evaporator and then to the generator, and a reverse flow mode for heat source input to the generator and then to the evaporator. Second, the first law of theoretical simulation characterizes the effects of the different operating modes on the heat transfer rates of each AHT component, the coefficient of performance (COP), and the steam generation rate. The experimental studies validate the theoretical simulation models; consequently, the results obtained herein lay a foundation of further investigation for the thermodynamic characteristics of the steam generating AHT system to maximize the operating performance.

With improved short-term surgical outcomes, laparoscopic distal gastrectomy has rapidly gained popularity. However, the safety and feasibility of laparoscopic total gastrectomy (LTG) has not yet been proven due to the difficulty of the technique. This single-arm prospective multi-center study was conducted to evaluate the use of LTG for clinical stage I gastric cancer. Between October 2012 and January 2014, 170 patients with pathologically proven, clinical stage I gastric adenocarcinoma located at the proximal stomach were enrolled. Twenty-two experienced surgeons from 19 institutions participated in this clinical trial. The primary end point was the incidence of postoperative morbidity and mortality at postoperative 30 days. The severity of postoperative complications was categorized according to Clavien–Dindo classification, and the incidence of postoperative morbidity and mortality was compared with that in a historical control. Of the enrolled patients, 160 met criteria for inclusion in the full analysis set. Postoperative morbidity and mortality rates reached 20.6% (33/160) and 0.6% (1/160), respectively. Fifteen patients (9.4%) had grade III or higher complications, and three reoperations (1.9%) were performed. The incidence of morbidity after LTG in this trial did not significantly differ from that reported in a previous study for open total gastrectomy (18%). LTG performed by experienced surgeons showed acceptable postoperative morbidity and mortality for patients with clinical stage I gastric cancer.

In this study, we synthesized cross-linked poly methyl methacrylate beads and cross-linked fluorinated poly methacryalte copolymer (F-cPMMA) beads by the dispersion polymerization method with methyl methacrylate monomer, ethylene glycol dimethacrylate, and 2,2,2-trifuloroethyl methacrylate. The size of cross-linked PMMA and F-cPMMA beads was about 100 nm. Then we developed a new geometrical high-hydrophobic film by embedding the F-cPMMA nanobeads on polyurethane (PU) film. The PU film containing fluorinated poly methacryalte copolymer beads showed a greater hydrophobic property than the non-fluorinated one in the range of 1–10 wt.%. For the purpose of industrial application of the PU films, we applied 0.1–1 wt.% of beads on the fabric by the laminating method. The PU film containing 1 wt.% of fluorinated poly methacryalte copolymer beads, which was laminated onto nylon fabric, showed the best performance of hydrophobic property (water contact angle, 79°) and moisture vapor transmission rate (8797 g·m–2·24 h).

The applications of electronic expansion valves in high temperature heat pump have increased rapidly. However, correlations for predicting R245fa mass flow rate through electronic expansion valves in high temperature heat pump are very limited in open literatures. In this study, mass flow rate characteristics of R245fa refrigerant flowing through electronic expansion valves with different operational conditions are studied experimentally, and empirical correlations are proposed based on the experimental data. The results reveal that the mass flow rate increases with increasing opening degree, condensation temperature, subcooling, and orifice diameter. Based on a modified single phase orifice equation, two empirical correlations are proposed by using the power-law correlation and the polynomial fit correlation, and over 92% of the predicted data deviate from the experimental data within ±15%.

To build an eco-friendly and sustainable energy ecosystem, research pertaining to absorption systems that can utilize waste heat from various industries is garnering attention. Among the elements of the absorption system, the phenomenon of heat and mass transfer in the absorber is complicated, and the predictive performance of existing absorber correlations is insufficient for universal use. Artificial neural network models are being considered as alternatives to existing methods in various fields. However, there is still a need for conventional correlations that allow easy analysis of physical relationships. In this study, rather than developing a model to classify or predict with an artificial neural network, it is used to analyze the collected experimental data. This method is expected to contribute to the easier development of more accurate correlations. Using the learned artificial neural network model, off-trend data organization, key parameter determination, and trend investigation for each parameter are performed. Based on the results of this investigation, a universally usable correlation for predicting absorber heat transfer is developed. The correlation, which can integrate the experimental data of nine published papers, is reviewed; it is demonstrated that the investigation results are consistent with the experimental data, with an error of approximately 22%.

Waste heat is a form of renewable energy discarded into the atmosphere. Waste heat-driven absorption systems (i.e., heat pumps and refrigeration systems) have attracted attention as district heating and cooling systems. This study proposes a waste heat-driven hybrid lithium bromide-water absorption system for the simultaneous generation of available steam and refrigeration effects. The proposed system is a form of the combined closed thermal cycle between the sub-heat pump and the sub-refrigeration system. It shares a generator and condenser, which allows the system to be more compact and flexible. We first present a description of the proposed system, designed for a cooling capacity of 350 kW with a steam generation rate of 200 kg/h. Our preliminary study proposed a pilot-scale system to clarify the flexible and simultaneous control means of the heating and cooling capacities by partially distributing the flow rate of the LiBr solution entering each sub-cycle. In addition to the results from the preliminary study, the present work examined the effect of part-load conditions on the operating parameters of the hybrid absorption system. The results showed that the coefficient of performances of sub-refrigeration and sub-heat pump cycle were approximately 0.787 and 0.658, respectively, and as a result, the total coefficient of performance of 0.463 was achieved. The theoretical model was validated by the experimental data, and the payback analysis was suggested to assure the economic validity of the proposed system. It was noted that the proposed hybrid absorption system demanded high initial facility cost than the comparison groups, but a payback of 2.79 and 2.36 years was evaluated because of the use of low-grade energy.

In the authors’ previous work, an embossed plate heat exchanger was proposed to the adsorption bed and results showed that the plate heat exchanger adsorption chiller had a lower Coefficient of performance (COP) but higher Specific cooling power (SCP) than those of a fin-tube type adsorption chiller, which shows high potential to resolve one of the most serious disadvantages of the adsorption cooling system, i.e., system size. However, only one section of the repeating embossed pitch plate was used and a uniform inlet flow condition was applied, which might have caused a distortion in estimated performance. We have reassessed the embossed plate heat exchanger adsorption bed by including the end effect to examine the real benefit of the proposed heat exchanger. The result showed that SCP was not significantly changed, while a 66.4 % increase in COP was observed. The proposed embossed plate heat exchanger adsorption bed is expected to provide advantages in both COP and SCP compared to a fin-tube type adsorption bed.

The absorber is one of the most important components in the LiBr-water absorption heat transformer (AHT) because it has the largest heat transfer area, and its performance significantly influences the overall system efficiency. Nevertheless, studies on absorbers used at the high-pressure level have not progressed. In this study, the horizontal tube falling film absorbers were constructed by introducing three types of heat transfer tubes (copper bare, copper-nickel bare, copper-nickel floral). The combined effects of the tube structure and material on the heat transfer performance of the absorber were experimentally investigated under the operating conditions of the single-stage AHTs. The experimental results showed that the film Reynolds number of 50 was optimal for the absorbers used in this study. At that point, the overall heat transfer coefficients of the copper bare tube, the copper-nickel bare tube, and the copper-nickel floral tube were 1,484, 1,448, and 1,299 W/m2 K, respectively. In addition, the heat transfer performance of the bare-type tubes was superior to that of the floral tube, except the under the low film Reynolds number. The empirical correlations of the Nusselt number for three types of heat transfer tubes were derived based on the experimental results and were predicted the data within the standard errors of 3.79–5.57 %.

In this paper, the mass flow rate characteristics of R245fa refrigerant flowing through electronic expansion valves (EEV) under varying operating conditions are studied experimentally. It is found that the mass flow rate increases with increasing EEV opening, condensing temperature, subcooling temperature, and orifice diameter. Based on the measured experimental data, two empirical correlations for mass flow rate prediction of R245fa through EEVs are proposed using the power-law correlation and the polynomial fit correlation. Predicted data of the polynomial fit method showed more consistency with the experimental results compared to that of power-law correlation, and 96.6% of the predicted mass flow rates deviate from the experimental data within ±10%.

In this paper, heat transfer characteristics of fin-tube heat exchanger and primary surface heat exchanger (PSHE) used in waste heat recovery were investigated experimentally. The flow in the fin-tube heat exchanger is cross flow and in PSHE counter flow. The variations of friction factor and Colburn j factor with air mass flow rate, and Nu number with Re number are presented. Various comparison methods are used to evaluate heat transfer performance, and the results show that the heat transfer rate of the PSHE is on average 17.3% larger than that of fin-tube heat exchanger when air mass flow rate is ranging from 1.24 to 3.45 kg/min. However, the PSHE causes higher pressure drop, and the fin-tube heat exchanger has a wider application range which leads to a 31.7% higher value of maximum heat transfer rate compared to that of the PSHE. Besides, under the same fan power per unit frontal surface, a higher heat transfer rate value is given in the fin-tube heat exchanger.

In studies addressing performance degradations owing to frost formation on heat exchangers, the frost thickness is considered an important parameter. The most commonly used method for measuring frost thickness comprises capturing and analyzing an image. However, relatively few studies have investigated the most reasonable method for deriving frost thickness by analyzing an image. In current measurement techniques, it is difficult to quantitatively determine which methods have less error relative to the true value in a complex shape. Therefore, this study attempted to recommend a more reasonable method, based on analysis of various aspects. First, the fundamental concept of image processing was described in detail. Then, the effects of thresholding algorithms, threshold application algorithms, and the determination of the number of segments on the frost thickness were investigated. Based on the results, an appropriate image processing method for measuring frost thickness was recommended. The frost thickness obtained by this method was well-measured, with an uncertainty of approximately 0.18 mm.

A parametric study on a heat-pipe type adsorption chiller with SWS-1L (mesoporous silica gel impregnated with CaCl2) and water pair was conducted using a numerical method in this research. A heat pipe that is in direct contact with the adsorbent is applied to the adsorption chiller to improve the heat transfer capacity of the adsorption bed. A feasibility study was performed on the heat-pipe type adsorption bed with a single layer. The Coefficient of performance (COP) and the Specific cooling power (SCP) were 0.231 and 844.8 W/kg, respectively. These values are lower than the system performance values of the existing fin-tube type adsorption bed. However, when the number of bed layers was increased to seven, the COP and SCP of the heat-pipe type adsorption bed were 0.520 and 752.4 W/kg, respectively. These values are 5.25 % and 39.8 % higher than the COP and SCP, respectively, of the fin-tube type adsorption bed. These findings indicate that the heat-pipe type adsorption bed can potentially address the disadvantage caused by the system size of the adsorption chiller. A parametric study was also conducted for six design parameters, namely, number of layers, heat pipe pitch, heat pipe radius, fin width, fin spacing, and hot water temperature.