用渗滤理论研究乙基纤维素骨架片的最适压片力范围

目的 用渗滤理论研究制备阿司匹林 乙基纤维素骨架片的最适压片力范围。方法 使用不同的压片力(3～ 30kN)制备了含阿司匹林 40 %的阿司匹林 乙基纤维素骨架片 ,测定了溶出曲线 ,用Higuchi方程和Ritger Peppas方程对溶出数据进行拟合。将拟合的Higuchi方程的斜率b值和计算得到的片剂的孔隙率ε,代入渗滤理论推导出的公式中 ,可计算出表观扩散系数D和片剂溶出性能参数 β ,分别以D对ε及 β对ε回归 ,可得到临界孔隙率εc,由 β ε,D ε和 β ε0 曲线可推知最适压片力范围。结果 压片力在 9～ 18kN时 ,药物释放遵从Higuchi模型方程 ,片剂以骨架扩散机制释药 ,且释药速度适中 ,因此 9～ 18kN为最适压片力范围。低于 9kN时 ,片子的初始孔隙率太大 ,药物溶出过快 ;高于 18kN时 ,药物溶出过慢 ,呈异常扩散机制释放药物。结论 渗滤理论可较清楚地阐明阿司匹林骨架片的释药机制 。

正畸牙移动中的差动力

差动力的概念自从在正畸界提出以来,已成功地应用于细丝弓技术中,得到了满意的临床矫治效果,但多年来仍是人们争论的焦点。本文回顾了差动力概念的提出及在细丝弓技术中的应用,综述了不同学者对差动力和最适力概念的不同观点以及差动力在方丝弓技术中的评价,认为不能片面地理解差动力的概念,应从牙根的大小、形态,牙移动的方向和类型,力量——时间类型,骨致密度等多方面综合理解差动力的概念。

闽—台近海渔业资源MSY和fMSY评估

本文根据１９７１－１９９４年福建和台湾省在闽－台近海的渔捞统计资料，以１９９４年福建的单位功率渔捞效率为基准捕捞力量标准化，应用Ｓｃｈａｅｆｅｒ和Ｆｏｘ两种剩余产量模式估算闽－台渔业资源的ＭＳＹ和ｆＭＳＹ，估算结果ＭＳＹ为１３０．８６万吨，ｆＭＳＹ为１０５．６１万ＫＷ。１９９４年实际渔获量和捕捞力量分别达１６０．８８万吨，１７１．２９万ＫＷ，超过了ＭＳＹ和ｆＭＳＹ的估算值。

An Improved Design of Spiral Groove Mechanical Seal

The coupling effect among the flow of fluid film, the frictional heat of fluid film and the thermal deformation of sealing rings is inherent in mechanical seals. The frictional heat transfer analysis was carded out to optimize the geometrical parameters of the sealing rings, such as the length, the inner radius and the outer radius. The geometrical parameters of spiral grooves, such as the spiral angle, the end radius, the groove depth, the ratio of the groove width to the weir width and the number of the grooves, were optimized by regarding the maximum bearing force of fluid film as the optimization objective with the coupling effect considered. The depth of spiral groove was designed to gradually increase from the end radius of spiral groove to the outer radius of end face in order to decrease the weakening effect of thermal deformation on the hydrodynamic effect of spiral grooves. The end faces of sealing rings were machined to form a divergent gap at inner radius, and a parallel gap will form to reduce the leakage rate when the thermal deformation takes place. The improved spiral groove mechanical seal possesses good heat transfer performance and sealing ability.

Adsorption of Chlortetracycline from Water by Rectories

The removal of antibiotics from water by clay minerals has become the focus of research due to their strong adsorptive ability. In this study, adsorption of chlortetracycline (CTC) onto rectories was conducted and the effects of time, concentration, temperature and pH were investigated. Experimental results showed that adsorption equilibrium was reached in 8 h. Based on the Langmuir model, the maximum adsorption capacity of CTC on rectories was 177.7 mg·g 1 at room temperature. By the study on adsorption dynamics, it is found that the kinetic date fit the pseudo-second-order model well. The adsorption of CTC by rectories is endothermic and the free energy is in the range of 10 to 30 kJ·mol 1 . The pH value of solution has significant effects on adsorption and the optimal pH is at acidity (pH 2-6). At concentration of 2500 mg·L 1 , the intercalated CTC produces an interlayer space with a height of 1.38 nm, which is 1.12 nm in raw rectories, suggesting that the adsorption occurs between layers of rectories.

Screening and identification of cellulose-degradation strain M1 and its characteristics of cellulase

In this paper, in order to get the target microbe which has high cellulose bio-degradation ability, we collected soil samples from environment rich in cellulose. Carboxymethyl cellulose sodium gel plate and filter paper plate were used for microbe screening, and finally we got a strain named MI which has the highest cellulase producing ability, and it has been identified as Penicilium oxalicum by morphological and molecular biological identification. We have studied cellulose degradation ability of this strain under different conditions such as pH value, temperature and inoculating time. The results showed that CMCase which belongs to acid enzyme, could achieve its maximum enzyme activity 489.96 U/ml when the optimal pH value was 4. The FPAase could achieve its maximum enzyme activity 1,595.45 U/ml when the optimal pH value was 4, too. The optimal ferment temperature of CMCase is 50℃ when achieved the maximum of enzyme activity at the second day, whereas the FPAase could reach its tip top on the third day, So the optimal ferment temperature of FPAase is also 50℃.

Adaptive robust output force tracking control of pneumatic cylinder while maximizing/minimizing its stiffness

The system considered in this work consists of a cylinder which is controlled by a pair of three-way servo valves rather than a four-way one.Therefore,the cylinder output stiffness is independently controllable of the output force.A discontinuous projection based adaptive robust controller (ARC) was constructed to achieve high-accuracy output force trajectory tracking for the system.In ARC,on-line parameter adaptation method was adopted to reduce the extent of parametric uncertainties due to the variation of friction parameters,and sliding mode control method was utilized to attenuate the effects of parameter estimation errors,unmodelled dynamics and disturbance.Furthermore,output stiffness maximization/minimization was introduced to fulfill the requirement of many robotic applications.Extensive experimental results were presented to illustrate the effectiveness and the achievable performance of the proposed scheme.For tracking a 0.5 Hz sinusoidal trajectory,maximum tracking error is 4.1 N and average tracking error is 2.2 N.Meanwhile,the output stiffness can be made and maintained near its maximum/minimum.

上颌尖牙牙根面积与牙体大小的关系

本文测量了５０颗完整上颌恒尖牙的牙根面积及牙体大小各指标，将测量结果输入微机，发现牙根面积变异范围较大，与牙体全长和根长存在高度正相关，与牙冠大小无关，并建立了线性回归模型，利用它可以在临床上预测牙根面积，以便确定矫治力。