A Study of the Heat Transfer Characteristics of an FC-72(C6F14) Two-Phase Closed Thermosyphon with Helical Grooves on the Inner Surface

This study is a fundamental work performed to obtain basic information about designing two-phase closed thermosyphons with a working fluid of FC-72 (C₆F₁₄). FC-72 is a kind of alternative refrigerant designed to be chemically safe and more environmentally friendly than any other conventional CFC refrigerants.

To obtain experimental data on operational performances of a FC-72 two-phase closed thermosyphon, an experimental model was designed and manufactured with a micro fin groove copper tube with an outside diameter of 22.2 mm for its container, on which a series of operational performance tests were conducted. Its maximum capacity of heat transport rate was designed to be about 300–400 W. The focus was given to investigate the effects of such parameters as micro fin grooves and fill charge ratios on operational performances of the FC-72 two-phase closed thermosyphon. The experimental data on phase change heat transfer coefficients and heat transport limitations were compared with some corresponding correlations, and a couple of measures that would help to predict operational performances were suggested with some physical explanations.     

残留复发性肝肿瘤射频消融治疗——超声造影的应用价值

【摘要】 目的 探讨对比增强超声（CEUS）在肝脏残留复发性恶性肿瘤进行射频消融（RFA）治疗的临床应用。方法 517例原发性肝癌（HCC）、肝转移癌患者经各种治疗后残留或局部复发拟行RFA治疗,共619个病灶为研究对象。复发HCC 281例290灶,病灶大小平均（3.4 ± 1.5）cm,其中CEUS引导治疗组150例154灶,常规超声引导组131例136灶。另复发肝转移癌236 例329 灶,病灶大小平均（3.1 ± 1.3）cm,其中CEUS引导治疗组152例198 灶,常规超声引导组84例131灶。结果 复发HCC CEUS组与常规组治疗结果比较:1个月肿瘤灭活率分别为96.1%和89.7%（P = 0.032）;肿瘤局部复发率各为9.7%和17.6%（P = 0.049）;两组间差异均有统计学意义。复发肝转移癌CEUS组与常规组治疗结果比较:1个月肿瘤灭活率88.4%和87.0%（P = 0.712）;肿瘤局部复发率16.7%和23.7%（P = 0.117）,两组间差异均无统计学意义。结论 CEUS 指导RFA治疗复发HCC,可有效提高早期灭活率,降低局部复发。     

Relation between etching profile and voltage–current shape of sintered SiC etching by atmospheric pressure plasma

Sintered silicon carbide (SiC) was etched by a dielectric barrier discharge source. A high voltage bipolar pulse was used with helium gas for the plasma generation. One stable filament plasma was generated and could be used for SiC etching. As the processing gas (NF₃) mixing rate increased, the width and depth of the etching profile became narrower and deeper. The differentiated V–Q Lissajous method was used for measuring the capacitances (C_eq) of the electrode after the plasma turned on. The width of the etching profile was proportional to C_eq. As the current peak value I_smx of the substrate current increased, the volume removal rate of SiC increased. The etch depth was proportional to the ratio of I_smx to C_eq. Additionally, because of the different characteristics of the plasma disks on SiC substrate by the voltage polarity, the etching profile was unstable. However, in high NF₃ mixing process, the etching profile became stable and deeper.     

Computational study on influence of RF shielding box on inductance of coil

Despite the fact that a radio frequency (RF) shielding box affects a coil inductance used in matching network, RF engineers have used a coil inductance measured in open space on designing matching networks since it is difficult to precisely measure the coil inductance within the RF shielding box. In this work, we investigate the influences of the RF shielding box on the coil inductance via a 3D full electromagnetic wave simulation. Simulation results shows that the coil inductance decreases from -6.0% to -11.9% compared with its ideal inductance depending on coil positions within the RF shielding box. Both inductive and capacitive coupling between the coil and surfaces of the RF shielding box contribute to the reduction of the coil inductance. We expect that these results would be useful for those who design RF matching networks.     

EFFECT OF GROWTH TEMPERATURE AND MEDIA ON INACTIVATION OF LISTERIA MONOCYTOGENES BY CHLORINE

The objective of this study was to determine the effect of growth environment on the susceptibility of Listeria monocytogenes to inactivation by hypochlorite sanitizer. Cells were grown in tryptic soy broth (TSB) at 35, 21, and 6°C and in 1:15 dilution of TSB (low nutrient medium, LNM) at 35°C. Late exponential phase cells were harvested, washed, and exposed to a 1 ppm sodium hypochlorite solution for periods up to 5 min. After 30 s exposure, cells grown at 35°C in TSB were reduced in number by 2.1 ± .3, at 21°C, 3.1 ± .3 and at 6°C, 3.4 ± .3 log units. After 30 s exposure to 5 ppm free chlorine cells grown at 35°C in TSB were reduced in number by 5.2 ± .2 and in LNM by 3.1 ± .1 log units. These data demonstrate that growth environment has a significant effect on chlorine inactivation of L. monocytogenes.     

Antioxidant Effects of Carnosine and Phytic Acid in a Model Beef System

Antioxidant and color stability effects of carnosine and phytate were compared in a fresh beef model system and in cooked beef. Both compounds increased the rate of pH decline in pre-rigor muscle. Phytate also increased the rate of post-mortem glycogen catabolism. Both antioxidants inhibited metmyoglobin formation in raw samples during storage. Phytate was more effective than carnosine for inhibition of lipid peroxidation. Heme iron content was negatively related to lipid peroxidation in cooked beef (r=–0.92). Phytate was also more effective for inhibition of iron release from heme during cooking. Phytate is recommended over carnosine as an effective antioxidant in cooked meats.     

CLONING, EXPRESSION AND CHARACTERIZATION OF NOVEL LECTIN FROM ORYZA SATIVA

A lectin gene homolog of Oryza sativa was successfully cloned and expressed in Escherichia coli. The deduced amino acid sequence of the protein product showed a significant similarity with known chitin‐binding lectins. Most of the recombinant lectin was found in an insoluble aggregated form as inclusion bodies and only a small part was in the culture medium in a soluble active form. Functional recombinant lectin was recovered from the inclusion bodies by solubilization with 8 M urea in Tris/HCl buffer, pH 7.0 and renaturation by 10‐fold dilution in the same buffer. The recombinant lectin with His‐tag was simply purified to homogeneity by the process of affinity chromatography and was obtained with a yield of 6–8 mg/L culture. The recombinant lectin was a homo‐dimer composed of 22 kDa. The hemagglutination activity of the recombinant lectin was optimal at pH 4.0–7.0 and it was very sensitive to inhibition by N‐acetylneuraminic acid and thyroglobulin.     

Experimental and thermodynamic investigations on MnO-SiO_2-Al_2O_3-MnS system

MnO-SiO₂-Al₂O₃-MnS oxysulfide system has been investigated by experimental phase diagram and activity measurement coupled with thermodynamic modeling.Phase equilibria of the MnO-MnS,MnO-SiO₂-MnS, MnO-Al₂O₃-MnS and MnO-SiO₂-Al₂O₃-MnS systems under low oxygen partial pressure have been experimentally investigated for the temperature range of 1 185 to 1 500℃using equilibration and quenching techniques. Equilibrium phases were analyzed by scanning electron microscope,electron probe X-ray microanalysis（EPMA）, and differential thermal analysis（DTA ）.Phase diagrams were successfully constructed for the systems investigated.Two ternary compounds in the MnO-SiO₂-MnS system were found.Activities of MnO and MnS in MnO-SiO₂-Al₂O₃-MnS liquid oxysulfide solution from very low sulfur concentration to high sulfur concentration at solid MnS saturation were investigated employing gas/liquid/Pt - Mn alloy under controlled atmosphere at 1 500℃.As X（SiO₂）/（X（MnO） + X（SiO₂）） increases in liquid oxysulfide solution,activity coefficient of MnO decreases while that of MnS increases.As X(AlO_1.5) increases,the activity coefficient of MnS increases while no remarkable change was observed for the activity coefficient of MnO.Quantitative analysis of the thermodynamic properties of the oxysulfide solution as well as phase diagram of the system was also earned out by employing the Modified Quasichemical Model in the quadruplet approximation.In view of inclusion utilization for free - cutting steel,it might have an advantage to decrease the Al₂O₃ content and increase the MnO/SiO₂ ratio.     

AN INVESTIGATION ON THE EFFECT OF MANGANESE SPECIFICATION IN BASIC OPEN HEARTH PROCESS

本文结合生产研究了鞍钢碱性平爐冶炼重轨和无缝等碳素镇静钢的锰制度.研究结果指出:就上述鋼种而言,熔炼过程中的锰制度对钢中氧、硫含量以及轧制的成品質量並没有实际影响,换句话说,并没有必要规定熔池含锰量高於一定水平(>0.15—0.2%Mn).相反地,熔池含锰较高或在熔炼过程中加入锰铁均使降碳速度趋於缓慢,从而延长了熔炼时间.因此,只要高炉铁水中含硫量能够合乎规定,用低锰生铁作原料对炼钢並无害处.通过高爐生产数据分析,说明在鞍钢的操作条件下完全有可能生产含锰低而含硫合乎上述规定的铁水,应该认为用低锰生鉄冶炼重轨和无缝类型的优質鋼是切实可行的.     

ON THE IMPROVEMENT OF THE QUALITY OF BALL-BEARING STEEL L THE EFFECT OF SMELTING AND CASTING PRACTICE ON NON-METALLIC INCLUSIONS IN BALL-BEARING STEEL

本文是提高滚珠轴承钢质量研究工作的第一部分。研究了碱性电弧炉内不同脱氧制度和浇铸条件对于钢中非金属夹杂物类型和数量的影响设及冶炼和浇铸过程中夹杂物的变化。 试验结果指出,采用下列操作制度可以显著改善滚珠钢中非金属夹杂物: 扒氧化渣后用硅锰合金预脱氧,然后用电石直接造电石渣,保持40分钟以上,还原后期用硅铁粉或电石继续进行扩散脱氧,出钢前炉渣必须变白,采用先出渣后出钢的办法,使渣钢在盛钢桶内得到很好的混合,进一步改善钢中非金属夹杂物。加铝量应在0.5公斤/吨以上。 结果证实,使用焦油处理过的优质盛钢桶内衬砝和汤道砝可以减少外来夹杂物。钢中氮化钛的来源是铁合金中含钛,所以在冶炼优质滚珠钢时应该选用不含钛的铁合金。