卖粮不应再难

经济师联谊会顾问,86年高龄的原中国科协书记处书记王文达同志关心今年粮油收购,向社会发出呼吁、语重心长、望有关部门重视并采取措施认真解决。

读者的希望

《北方音乐》编辑部: 在进入新的一年时,我,一个远在千里之外的江西读者,真诚地向贵刊提出几条不成熟的建议: 一、封面摄影不但要注明摄影者的姓名,而且要说明所摄的是什么。 二、贵刊的歌头题花设计较活泼,但有些题图的设计不太切合主题。

Missing Via Mechanism and Solutions

Missing via has been a defect in semiconductor manufacturing,especially of foundries. Its solution can be rather attractive in yield improvement for relatively mature technology since each percentage point improvement will mean significant profit margin enhancement. However, the root cause for the missing via defect is not easy to determine since many factors,such as, defocus, material re-deposition, and inadequate development,can lead to missing via defects. Therefore, knowing the exact cause for each defect type is the key. In this paper, we will present the analysis methodology used in our company. In the experiments,we have observed three types of missing vias. The first type consists of large areas, usually circular,of missing patterns,which are primarily located near the wafer edge. The second type consists of isolated sites with single partially opened vias or completely unopened vias. The third type consists of relatively small circular areas,within which the entire via pattern is missing. We have first tried the optimization of the developing recipe and found that the first type of missing via can be largely removed through the tuning of the rinse process, which improves the cleaning efficiency of the developing residue. However, this method does not remove missing via of the second and third type. We found that the second type of missing via is related to local defocus caused by topographical distribution. To resolve the third type of missing via defects, we have performed extensive experiments with different types of developer nozzles and different types of photomasks,and the result is that we have not found any distinct dependence of the defect density on either the nozzle or the mask types. Moreover, we have also studied the defect density from three resists with different resolution capability and found a correlation between the defect density and the resist resolution. It seems that,in general, lower resolution resists also have lower defect density. The results will be presented in the paper.

Fabrication and anodic polarization behavior of lead-based porous anodes in zinc electrowinning

A new type of lead-based porous anode in zinc electrowinning was prepared by negative pressure infiltration. The anodic polarization potential and corrosion rate were studied and compared with those of traditional fiat anodes （Pb-0.8%Ag） used in industry. The anode corrosion rate was determined by anode actual current density and microstructure. The results show that the anodic oxygen evolution potential decreases first and then increases with the decrease of pore diameter. The anodic potential decreases to the lowest value of 1.729 V at the pore diameter of 1.25-1.60 mm. The porous anode can decrease its actual current density and thus decrease the anodic corrosion rate. When the pore diameter is 1.60-2.00 mm, the anodic relative corrosion rate reaches the lowest value of 52.1%.

Solubilization of small molecules from coal and the resulting effects on the pore structure distribution

The solubilization of small molecules from coal by solvent extraction and the resulting effects on the pore distribution of a low rank coal were studied. Samples were extracted, in succession, with petroleum ether and with CS2. Extract and residue fractions collected during the solubilization process were analyzed by FTIR and by surface area and porosimetry. The results show that an obvious inflection point exists that allows separating the dissolution sequence into stages. Small molecules are first extracted from the free state, then molecules trapped in micropores are extracted and, finally, molecules trapped in the coal-matrix network are extracted. This is indicated from the extraction yield curves. Chain-like carbonyl compounds, -OH (or -NH) containing compounds that are hydrogen bonded and phenolics dominate the petroleum ether extracts. Chain-like carbonyl components and ether compounds (aliphatic ethers and aromatic ethers) dominate the CS2 extracts. A solvent dissolution mechanism and the effect of small molecule extraction on the pore structure are put forward. Diffusion, dissolution, pore opening, pore shrinking or even collapsing caused by swelling, creating of new micropores, pore opening and, finally, colloidallization of some micropores occurs. In the later stages of the extraction the internal structure of the coal is colloidallized due to swelling and the pore number or volume is greatly reduced.

Mechanism and experiment of substituting high drainage roadway with directional long drilling group to extract pressure-relief gas

By establishing the numerical model in the vertical plane and the similar model in the horizontal plane of gas flow in goaf, the influence of high drainage roadway or drilling on the gas seepage field was analyzed, and the extraction mechanism was clarified. On this basis, the academic thought of directional long drilling group instead of high drainage roadway was put forward. And then using complex function theory, the permeation mechanical model of drilling group with circle distribution in the mining-induced fracture zone was established to explore the coupling relationship between the drilling quantity, extraction volume and the equivalent extraction rate of single drilling. Finally, combined with the concrete geological production conditions, the main parameters of directional long drilling group were determined. The distance between the drilling group center and the air-return roadway is 24 m, the height is 18 m, and the three drillings are in an approximate equilateral triangle distribution with a space of 8 m. The equivalent extraction square is 4.15 m2. It is shown that the effect of directional long drilling group is evident. The gas content in the upper comer is controlled below 0.95%, the content in the tail roadway is kept below the alarm value, and the content is over 50% in the drill, realizing the secure and effective extraction of coal and gas.

Reconsider Confucius＇ enlightening reflection： Implications on heuristic teaching

Western heuristic teaching method was originated from Socrates who initiated the teaching mode of ＂teachers ask, students answer＂. A distinctive feature of this mode was that teachers were the decisive factor in the process of teaching and learning, who raised the questions at the very beginning and gave conclusions in the end. On the contrary, oriental style of heuristic teaching method based itself on the principle that students put forward their puzzles and then asked the teachers for advice. This paper will reconsider Confucius enlightening reflection and probe into how to develop students＇ ability of thinking by questioning strategies in the heuristic teaching methodology.

The relationship between organic matter and specific surface area in <2 μm clay size fraction of muddy source rock

The adsorption of organic matter(OM)onto clay minerals has long been considered as a significant way of OM preservation in source rock.Here we analyzed the relationship between OM and the specific surface area(SSA)of <2μm clay size fraction isolated from 13 source rock cores collected from Dongying depression.Rock-Eval pyrolysis and N2 adsorption experiment were employed to probe the characteristics of OM and SSA(denoted SBET)in samples before and after OM extraction using trichloromethane.The results indicate that various kinds of OM occurrence coexist in clay size fraction and their contributions to hydrocarbon are different in each period of OM evolution.The occurrence and amount of OM affect the S BET of clay size fraction,and a nonlinear negative correlation between total organic carbon(TOC)and S BET can be recognized.The soluble OM(chloroform extract "A"),mainly stored in the pore space of clay size fraction,shows a negative correlation in amount with S BET.Our data also indicate that free hydrocarbon(S1)was stored mainly in the pore space and/or the surface of clay size fraction,whereas pyrolysis hydrocarbon(S2)was mingled mainly with clay minerals.Therefore,to understand various OM occurrences and their relationship with SBET in the clay size fraction is significant in the study of generation,accumulation,and migration of hydrocarbon in muddy source rock.

PDE-BASED MEDIAL AXIS EXTRACTION AND SHAPE MANIPULATION OF ARBITRARY MESHES

Shape skeletonization （i.e., medial axis extraction） is powerful in many visual computing applications, such as pattern recognition, object segmentation, registration, and animation. In this paper, the authors expand the use of diffusion equations combined with distance field information to approximate medial axes of arbitrary 3D differential properties. It offers an alternative solids represented by polygonal meshes based on their but natural way for medial axis extraction for commonly used 3D polygonal models. By solving the PDE along time axis, this system can not only quickly extract diffusion-based medial axes of input meshes, but also allow users to visualize the extraction process at each time step. In addition, the proposed model provides users a set of manipulation toolkits to sculpt extracted medial axes, then use diffusion-based techniques to recover corresponding deformed shapes according to the original input datasets. This skeleton-based shape manipulation offers a fast and easy way for animation and deformation of complicated mesh objects.

A feature extraction method for synthetic aperture radar(SAR) automatic target recognition based on maximum interclass distance

Synthetic aperture radar(SAR) automatic target recognition is an important application in SAR.How to extract features has restricted the application of SAR technology seriously.In this paper,a new feature extraction method for SAR automatic target recognition based on maximum interclass distance is proposed,which integrates class and neighborhood information.This method can reinforce discriminative power using maximum interclass distance,so it can improve recognition rate effectively.