This meta-analysis evaluates the impact of reducing crude protein (CP) levels in growing pig diets on manure nitrogen emissions to identify strategies for maximizing environmental benefits. A systematic search of PubMed, ISI Web of Science, and Scopus (2003 to 2024) yielded 56 observations from 10 studies. We employed random-effects models with restricted maximum-likelihood (REML) estimation and used Hedges’ g to calculate standardized mean differences (SMD). Additionally, meta-regression and broken-line regression analyses were conducted to investigate heterogeneity and emission breakpoints. The results indicate that low-protein diets significantly reduce both urinary nitrogen emissions (SMD = -5.09; p < 0.0001) and fecal nitrogen emissions (SMD = -0.79; p < 0.001). Substantial heterogeneity was observed for both fecal ($I^2$ = 81.6%) and urinary ($I^2$ = 81.7%) nitrogen emissions (p < 0.0001), highlighting the influence of varying study conditions. Broken-line regression analysis identified a significant breakpoint for urinary nitrogen emissions at 18.8% CP (p < 0.01), whereas no significant breakpoint was observed for fecal nitrogen emissions. Meta-regression analysis revealed that every 1% decrease in dietary CP was associated with increased supplementation of synthetic amino acids, including DL-methionine (p < 0.05), DL-tryptophan (p < 0.04), and L-threonine (p < 0.02), with L-lysine showing a tendency to increase (p = 0.10). Furthermore, economic analysis demonstrated that a moderate reduction to 15% CP, supplemented with four essential amino acids, yields a net cost saving of approximately $2.80 USD per metric ton; conversely, a drastic reduction to 13% CP incurs a net cost increase of approximately $14.30 USD per metric ton due to the high cost of valine and isoleucine. In conclusion, reducing dietary crude protein levels serves as an effective strategy for mitigating urinary nitrogen emissions, necessitating the precise supplementation of synthetic amino acids to balance environmental benefits with the nutritional requirements of growing pigs.

With high redox activity, superior conductivity, abundant pores, and large specific surface area, nitrogen-doped graphitic carbon featuring a hierarchically porous structure is regarded as ideal electrode material for supercapacitors. In this work, hierarchically porous nitrogen-doped graphitic carbon (PG-PZC50) was fabricated via non-solvent induced phase separation and high-temperature calcination processes. SEM images showed its three-dimensional network structure, with abundant macro- and mesopores distributed throughout. XRD and Raman spectra confirmed the phase purity and graphitic nature of the as-prepared material, while XPS revealed its surface elemental composition, especially the content and doping states of nitrogen atoms. The graphene oxide-induced three-dimensional network, combined with the mesoporous structure of metalorganic framework-derived N-doped carbon particles, creates abundant migration channels and a large adsorption surface area for the electrolyte ions. Benefiting from its hierarchically porous structure and high nitrogen-doping content, the formed PG-PZC50 reached high specific capacitances of 499.7 F g− 1 at 0.1 A g− 1 and 179.6 F g− 1 at 20 A g− 1. Notably, the material also demonstrated robust cyclic stability with no capacitance loss after 10,000 charge–discharge cycles. The proposed synthetic strategy provides new ideas for the facile and reproducible construction of nitrogen-doped graphitic carbon with 3D hierarchically porous structure and high capacitive performances.

본 연구는 축산업의 집약화로 인한 가축분뇨 과잉 문제를 해결하고, 이를 유기질 비료로 자원화하기 위해 계분 바이오차(CMBC)의 비료적 가치를 평가하였다. CMBC는 계분과 목질계 바이오매스를 80:20 비율로 혼합하여 400℃에서 2시간 열분해하여 제조하였으며, 이를 포트실험에 적용해 배추(Brassica rapa subsp. pekinensis) 생육, 토양 특성, 질소 이용효율에 미치는 영향을 분석하였다. 실험은 무처리(CN), 무기질비료(IF), 그리고 계분 바이오차(CMBC)를 3, 5, 7 및 10 t ha-1의 시용량으로 전량 기비 처리한 처리구(CMBC3, CMBC5, CMBC7 및 CMBC10)로 구성하였다. IF 처리구는 작물별 표준시비량을 기준으로 시용하였다. 수확 후 토양은 CMBC 시용량 증가에 따라 pH, EC, CEC, 유기물, 총질소, 유효인산이 유의하게 증가하는 경향을 나타내었고 특히 CMBC10 처리구의 pH는 무처리구 대비하여 5.86에서 7.67로 증가하였으며, EC는 0.19 dS m-1에서 6.91 dS m-1로 크게 상승하였다. 또한 유효인산은 86.3에서 1,959 mg kg-1까지 증가하여, 계분 바이오차의 인 공급 효과가 두드러졌다. 이와 함께 O.M, T-N 및 CEC 역시 각각 126%, 143% 및 268% 증가하여 토양 비옥도가 전반적으로 향상되었다. 생육은 CMBC5 처리구에서 339 mg plant-1로 가장 우수하였으며 IF 처리구 대비 생중량, 건중량, 구중의 둘레 및 엽수가 각각 20.6%, 15.5%, 2.8% 및 11.7% 증가하였다. 질소 흡수량 또한 CMBC5 처리구에서 가장 높은 것을 확인하였으며, 겉보기 질소 회수 효율(Apparent Nitrogen Recovery Efficiency, AE_N)과 농업적 질소 이용 효율(Agronomic Nitrogen Use Efficiency, ARF_N)은 CMBC3 처리구에서 최대치(28.6 kg N ha-1, 164%)를 기록하였다. 따라서 본 연구에서는 3~5 t ha-1의 계분 바이오차 시용이 배추 생육 증진, 토양 비옥도 개선 및 질소 이용효율 향상 측면에서 가장 효과적인 것으로 판단되었다. 이러한 결과는 계분 바이오차가 유기질 비료로써 실질적인 활용 가능성을 시사하며, 다양한 작물과 실제 농경지 조건에서의 효과를 검증하기 위한 추가적인 연구가 필요하다.

하수처리장의 안정성과 효율성의 향상을 위해 스마트 기술 도입이 요구되고 있으나, 운영 데이터베이스 구축에 있어 계측의 신뢰성과 연속성 확보에 어려움이 있다. 활성슬러지 모델은 하수처리장의 디지털트윈으로 활용되며, 유입수 성상이 동일하더라도 다양한 운전 조건에 대한 데이터를 생산할 수 있다. 본 연구에서는 실측 데이터와 시뮬레이터 기반 합성 데이터를 통합하여 하수처리장 질소 농도 예측 머신러닝 모델을 구축하였다. A2O 공정의 호기조를 대상으로 기체상 N2O 및 액상 NH4 + 농도를 측정하였으며, 내부반송량, 외부반송량 등 운전인자를 포함한 운영데이터베이스를 구축하고 분석하였다. 확보한 실측 데이터를 기반으로 운영 특성을 분석하고, Sumo4N 모델을 활용하여 다양한 운전 조건에서의 합성 데이터를 생성하였다. 이후 두 데이터를 통합하여 데이터 증강을 수행함으로써, 실측 데이터의 양적 한계를 보완하였다. 모델 학습을 위한 입력 변수로는 외부⋅내부 반송량, 폭기량, 온도, 유입 질소 부하, pH를 선정하였으며 호기조의 N2O, NH4 +과 방류수 TN 농도를 예측하기 위한 머신러닝 모델을 개발하였다. 모델 학습에는 Lasso Regression, Random Forest, k-NN, SVR 알고리즘을 적용하여 성능을 평가하였다. 그 결과 SVR 알고리즘이 모든 질소 성분 예측에서 가장 우수한 성능을 보였으며, 개발된 모델 모두 R² ≥ 0.75의 높은 예측 성능을 나타내었다. 이는 시뮬레이터 기반 데이터 증강을 통해 기체상 및 액상 질소의 통합 제어를 위한 머신러닝 모델 구축의 가능성을 시사한다.

메탄화 공정은 탄소 포집 및 활용(CCU) 기술의 하나로, 탄소중립 달성을 위한 핵심 기술이다. 본 연구는 메탄화 반응기 배출가스에서 생성가스인 메탄과 미반응 수소를 분리하기 위한 가스 분리 시스템 설계를 위한 사전 연구로, 소형 막 모듈을 이용한 2단 분리막 시스템을 설계⋅제작하고 시험 가스인 질소-수소 혼합가스에 대한 분리 성능을 실험적으로 평가하 였다. 1단 막 모듈에서는 질소-수소 혼합가스에 대한 혼합 가스 선택도를 측정하였으며, 1단 및 2단 막 모듈 모두에서 잔류 측과 투과 측의 목표 가스 회수율 및 순도를 분석하였다. 본 연구에서 수행한 국내 A사 막 모듈의 성능 분석 결과는 향후 메 탄화 반응 가스 분리 시스템 설계 및 최적화 연구의 기초자료로 활용될 수 있다.

Structural design and element doping are the research hotspots in the preparation of lightweight absorbers with high absorption performance and low filling rate. This study employs different temperature carbonization and etching techniques to prepare the structure of hollow nitrogen-doped carbon flowers (HNC) and evaluate their microwave absorption performance. At an ultra-low filler loading of 5 wt.%, the microwave absorption intensity of HNC-800 remains stable at -50 dB with a thickness of 3.2 mm. It is noteworthy that the HNC-800 achieved the broadest effective absorption frequency band at a matching thickness of 2 mm, with a bandwidth of 5.36 GHz (ranging from 12.4 to 17.76 GHz). Such remarkable broadband and reflection loss performance can be attributed to the synergistic effects of the hollow porous network structure, interface polarization, and dipole relaxation mechanisms. More significantly, the reduction of the radar cross-section (RCS) amounts to as much as 31.67 dB m2, and it has been attested to possess excellent adsorption efficacy in practical application scenarios. HNC-800, as an absorbing material, holds potential for broad application prospects.

Developing highly durable and active catalysts is essential for improving the performance and longevity of proton exchange membrane fuel cells (PEMFCs). In this study, we propose a novel strategy to enhance catalyst dispersion and stability by incorporating pyrrolic nitrogen-rich carbon (pNC) quantum dots into highly crystalline carbon supports. The introduction of pNC generates strong anchoring sites for Pt nanoparticles, facilitating uniform dispersion and minimizing aggregation, which are key factors in enhancing catalytic performance and durability. The synthesized Pt/CVC150 catalyst exhibited excellent oxygen reduction reaction activity, with a half-wave potential of 0.842 V and a limiting current density of 6.3 mA cm− 2. Under accelerated stress test conditions, the catalyst retained 61.4% of its initial peak power density after prolonged cycling, indicating enhanced durability. Furthermore, single cell testing confirmed its improved electrochemical activity and stability of the Pt/CVC150 catalyst in a practical PEMFC operating environment. These findings suggest that the incorporation of heteroatom-doped carbon moieties onto carbon supports represents a promising strategy for the development of nextgeneration PEMFC catalysts with enhanced performance and longevity.

This study presents, for the first time, a piezoelectric nanogenerators (PENG) model based on the nitrogen-doped carbon nanotubes (N-CNTs) array and demonstrates the ability of N-CNT to convert external oscillations into electrical energy. Molybdenum was proved to be a preferred material for the upper electrode due to its high corrosion resistance and the formation of ohmic contact at the interface with N-CNT. It was shown the operation of the PENG model in constant and pulsed modes. It was found that the output voltage of the PENG model increased linearly from 3 to 60 mV with an increase in the amplitude of the external mechanical influence from 3.5 to 95 μm and decreased from 54 to 26 mV with an increase in the frequency of external influence from 15 to 120 Hz due to an excess of the natural resonant frequency of the nanotubes. The experiments demonstrated that the power density of the N-CNT-based PENG model reached 12.63 μV/cm2. It was exhibited that the PENG model can be used not only as a nanogenerator for autonomous power supply of wearable electronic devices, but also as a highly sensitive deformation sensor. In addition, the clamping force of the upper electrode determines the frequency range of the PENG model. The obtained results open wide opportunities for practical application of vertically aligned N-CNTs for autonomous power supply of wearable electronic devices.

연근해 소형선박의 질소산화물(NOx)과 입자상물질(PM)의 배출 저감은 강화되는 해양환경 규제 대응을 위해 필수적이다. 본 연 구에서는 총톤수 21톤, 정격출력 367 kW(@1,800 rpm)의 고속디젤엔진을 장착한 연근해 소형선박에 배출저감설비(DPF+SCR)를 적용하여 해상실증 시험을 수행하였다. 가스상물질은 NOx Technical Code와 ISO 8178 기준을 준용한 장비를 사용하였으며 입자상물질(매연)은 국제 해사기구(IMO)에서 논의 중인 블랙카본 측정 방법 중 스모크미터를 이용하여 측정하였다. 황 함유량 0.03%S 이하 연료를 사용하여 20일 간 실제 운항 데이터를 모니터링하고, 모니터링 전·후 시험조건에 따라 1, 2차 성능시험을 수행하였다. 시험결과, NOx 저감효율은 62.0~97.8%, PM 저감효율은 93.0~97.4%를 나타냈으며, 배압은 60mbar 이하를 유지하였다. 운항 조건을 고려한 최적 저감효율은 70~80%이 며, 요소수 탱크 용량은 연료 저장 탱크 용량 대비 최소 4% 이상 요구된다. 본 연구는 연근해 소형선박의 NOx와 PM 동시 저감을 위한 배 출저감설비(DPF+SCR) 적용 가능성을 확인하였다.

The experiment was conducted to determine the effects of nitrogen fertilizer levels on seed production of Italian ryegrass (Lolium multiflorum Lam.) in mountainous regions of Gangwon Province. The 'Green Call' variety of Italian ryegrass was sown in Pyeongchang, Gangwon in September 2021. The experiment consisted of three nitrogen application levels (100, 120, and 140 N kg/ha) and was arranged in a randomized complete block design with three replications. Harvest was carried out on June 28. The plant height was tallest in the 140 N kg/ha treatment, but the difference was not statistically significant. Lodging resistance, disease resistance and winter hardiness showed no significant differences among treatments, although severe lodging occurred in all plots. The average spike length was 54.77 cm, with no significant difference among treatments, while the number of seeds per spike was highest in the 100 N kg/ha treatment. Seed yield increased with higher nitrogen levels, with an average of 2,820 kg/ha (based on air-dry weight). The average dry matter content of seeds and straw was 56.70% and 38.80%, respectively, with no significant differences among treatments. The average dry matter yield of residual straw after seed harvest was 4,144 kg/ha, with the highest yield observed in the 120 N kg/ha treatment. Meanwhile, the feed value of the harvested straw did not differ significantly among treatments. The average contents of ADF, NDF, CP, IVDMD, and TDN were 43.04%, 70.63%, 8.65%, 52.77%, and 54.88%, respectively. In conclusion, the optimal nitrogen fertilization level for Italian ryegrass seed production through autumn sowing in the mountainous areas of Gangwon Province was found to be 120 N kg/ha.