Thermal Stability Improvement of Vertical Conducting Green Resonant-Cavity Light-Emitting Diodes on Copper Substrates

Green light vertical-conducting resonant-cavity light-emitting diodes (RCLEDs) have been fabricated on a Cu substrate by the combination of laser lift-off and plating techniques. The structure of the RCLED/Cu is consisted of the InGaN-GaN multiple-quantum-well active layer between three layers of the dielectric TiO-SiO distributed Bragg reflector as a top mirror and an Al metal layer as a bottom mirror. It was found that the RCLED with Cu substrate presents superior thermal dissipation and a stable electroluminescence emission peak wavelength (507 nm) under a high injection current. It is attributed to the Cu substrate providing a good heat sink and effectively reducing the junction temperature.     

Catalytic Incineration of C2H5SH and Its Mixture with CH3SH over a Pt/Al2O3 Catalyst

Catalytic incineration is one of the cost-effective technologies to solve troublesome volatile organic compounds. However, some sulfur containing volatile organic compounds, such as ethyl mercaptan, may deactivate the Pt catalyst that is commonly used in the catalytic incineration process. This paper provides information on the poisoning effect of ethyl mercaptan. The catalytic incineration of ethyl mercaptan, typically emitted from the petrochemical industry, over a Pt/Al2O3 fixed-bed catalytic reactor was studied. The effects of operating parameters including inlet temperature, space velocity, C2H5SH concentration, O2 concentration, and catalyst size were characterized. Catalytic incineration on a mixture of C2H5SH with CH3SH was also tested. The results show that the conversions of C2H5SH increase as the inlet temperature increases and the space velocity decreases. For the temperature from 200–260°C, the higher the C2H5SH concentration is, the lower its conversion. The O2 concentration has a positive effect on the conversion of C2H5SH. C2H5SH has a poisoning effect on the Pt/Al2O3 catalyst, especially at lower temperature. The existence of CH3SH has no effects on the conversion of C2H5SH.     

Model reduction of digital systems using discrete Walsh series

This study discusses the application of discrete Walsh series expansion to reduce the order of a linear time-invariant digital system described byz-transfer function. The approach is based on matching the discrete Walsh spectra to determine both the coefficients of the denominator and numerator of the reduced model. The proposed method is simple for computation, can preserve the dynamic characteristic of the original model satisfactorily, and guarantees to have the same zero initial response as the original system.     

高效液相色谱法测定食醋中乳酸的不确定度评定

摘 要： 目的 建立高效液相色谱法测定食醋中乳酸的不确定度的数学模型。方法 根据JJF1059.1-2012《测量不确定度评定与表示》,从测量过程各步骤分析不确定度来源,并对已识别来源的不确定度影响进行评价和分析。结果 测量结果不确定度主演来源于乳酸标准溶液、试样溶液配制和液相色谱仪的定量重复性。当食醋中乳酸含量为48.49mg/g时,其扩展不确定度为1.34mg（k=2）。结论 该研究可为实验室评定食醋中乳酸含量的测定结果质量提供参考。     

热裂解-气相色谱-质谱法快速筛查和定量分析乳与乳制品中的4种微塑料

目的 建立热裂解-气相色谱-质谱法（pyrolysis-gas chromatography mass spectrometry, PY-GC-MS）快速筛查和定量分析乳与乳制品中的4种微塑料（microplastics, MPs）,防止原料、生产工艺、包装等过程带入微塑料残留。乳与乳制品中微塑料（microplastics, MPs）检测的热裂解-气相色谱质谱联用技术（pyrolysis-gas chromatography mass spectrometry, PY-GC-MS）。方法 以聚碳酸酯（polycarbonate, PC）、聚对苯二甲酸乙二醇酯（polyethylene terephthalate, PET）、聚酰胺6（polyamide 6, PA6）和聚酰胺66（polyamide 66, PA66） 4种微塑料粒子为例,采用红外光谱和粒度分析对微塑料形貌进行表征。考察了进样模式、裂解温度对裂解效果的影响,并对四种微塑料的特征定量峰进行比较并对4种微塑料的特征定量峰进行比较 ,最终选择单击式裂解模式,裂解温度600℃,4种微塑料的特征物质分别为双酚A、对苯二甲酸-2-苯甲酰氧基乙酯乙烯酯、己内酰胺和环戊酮。验证了裂解方法的稳定性和特异性,利用高温裂解产生的特征碎片离子进行定量分析。结果 本方法对四种微塑料检测的线性范围为本方法对4种微塑料检测的线性范围为2 μg ~64 μg ,检出限0.1 μg~1.2 μg,定量限0.3 μg~4.0 μg,平均加标回收率79.5%~96.0%,精密度1.74%~10.8%。结论 本方法适用于乳与乳制品中微塑料的检测,也可以进一步优化条件应用到其他类型的微塑料检测过程,作为微塑料浓度检测标准制定的参考方法。     

贻贝中微塑料检测的消解方法比较

目的 比较双壳贝类中微塑料检测常用的酸消解、碱消解、氧化消解和酶消解等方法,推荐适用于贝类中微塑料检测的通用型消解方式。方法 以常用的指示性双壳贝类贻贝作为研究对象,确定食品样品检测通用的消解条件。在这些条件下对聚苯乙烯（polystyrene,PS）、聚丙烯（polypropylene,PP）、聚碳酸酯（polycarbonate,PC）、聚乙烯（polyethylene,PE）、聚对苯二甲酸乙二醇酯（polyethylene terephthalate,PET）、聚酰胺6（polyamide,PA6）和聚酰胺66（polyamide,PA66）七种微塑料进行消解,考察不同条件下微塑料粒子消解前后重量、红外光谱、粒径分布和形貌特征的变化。结果 采用不同的消解方式对不同的微塑料影响不同,其中重量受影响较大的是PA6和PA66,在硝酸-高氯酸混合溶液和高氯酸-双氧水混合溶液中完全溶解损失,PC和PET在氢氧化钾溶液中损失严重。通过结构表征,PE、PA6和PC的粒径增加,PC的形貌结构发生彻底改变。结论 微塑料含量甚微的双壳贝类样品进行检测,推荐采用胃蛋白酶溶液和胰蛋白酶溶液进行消解;如需缩短消解时间,推荐采用双氧水在高温下消解。     

2017—2019年普洱市食品中化学污染物监测结果分析

目的了解2017—2019年普洱市食品风险监测中化学污染物状况。方法 2017—2019年在普洱市辖区内各区县农贸市场、商店等采集不同种类食品样本进行食品接触材料污染物、食品添加剂、兽药残留、元素、农药残留等项目的检测。结果 2017—2019年普洱市食品超标率分别为食品接触材料污染物32.00%、食品添加剂24.32%、兽药残留3.17%、元素3.03%、农药残留0.73%。结论普洱市常见食品中有部分化学污染物(五氯酚钠、含铝添加剂、铅、砷、强力霉素、恩诺沙星、甲拌磷、甲拌磷砜等)超标,对人体健康造成危害。各相关部门应加强监管。     

传统培养法与荧光PCR法检测弧菌的方法评价

目的比较标准检测方法与杜邦BAX System Q7快速检测方法检测副溶血性弧菌、霍乱弧菌和创伤弧菌。方法采用GB 4789.7—2013《食品微生物学检验副溶血性弧菌检验》、SN/T 1022—2010《进出口食品中弧菌霍乱弧菌检验方法》、DBS 13/004—2016《食品安全地方标准创伤弧菌检验》标准和杜邦BAX System Q7系统操作方法对1份同时污染副溶血性弧菌、霍乱弧菌和创伤弧菌的样品进行检测。结果BAX System Q7操作方法与标准操作方法检测结果一致,其中BAX System Q7可同时检测3种弧菌,用时20 h,而标准操作方法至少需要6 d。结论BAX System Q7检测方法与标准方法均具备高准确性,但相较于标准检测方法,BAX System Q7检测方法鉴定更快速、操作更简便,且3种弧菌可以同时鉴定。     

超高效液相色谱-四极杆/静电场轨道阱高分辨质谱法快速检测茶叶中草甘膦、草铵膦及其代谢物残留

摘 要：目的 建立一种非衍生化处理, 直接测定茶叶中草甘膦、草铵膦及代谢物的的快速分析方法。方法 茶叶样品经酸化的同体积甲醇-水进行提取, 经Oasis PRiME HLB 固相萃取柱通过式净化, 并通过超高效液相色谱-四极杆/静电场轨道阱高分辨质谱法对样品进行测定。结果 茶叶中草甘膦、草铵膦及代谢物在1.0~50 ng/mL的范围内, 线性关系良好(r2＞0.999), 平均回收率在83.7%~92.2%之间, 相对标准偏差低于10%, 检出限为0.01 mg/kg, 定量限为0.05 mg/kg。结论 此方法前处理简便快速, 且准确性好、灵敏度高, 可实现茶叶中草甘膦、草铵膦及其代谢物的快速筛查。     

Water bonding of 50-mm-diameter mirror substrates to AlGaInP light-emitting diode wafers

The feasibility of bonding 50-mm-diameter Si with a Au/AuBe mirror to AlGaInP light-emitting diode (LED) wafers is demonstrated. Wafer bonding over the entire wafer area is achieved while the metallic mirror still maintains high reflectivity. Using this technique, the mirror-substrate AlGaInP LEDs are fabricated across an entire 50-mm wafer. The test data show that 98% of the dice with operating voltages <2.2 V at 20 mA and 85% of the dice with luminous intensity in the 130∼140 mcd region. The wafer-bonded mirror-substrate LED lamps operating at 626 nm can emit 3 lm at 20 mA with a forward voltage of 2 V, corresponding to a luminous efficiency of 74 lm/W. Moreover, they present a peak power efficiency of 21% with 4 mW output at 10 mA (1.9 V). Essentially no degradation is observed for these LEDs after 2000 h stress at 80°C and 50 mA (55.6 A/cm²). The results indicate the mirror-substrate AlGaInP LEDs of highly reliable and efficient performance.