种植修复10分钟及1个月后基台中央螺丝扭矩丧失情况的横断面研究

目的:本横断面研究采用4种不同的种植系统修复单颗前磨牙或磨牙缺失,观察种植修复体戴入,基台中央螺丝初次旋紧后的10 min及1个月,基台中央螺丝扭矩丧失的情况。方法:2021年7月~2023年6月于北京大学深圳医院口腔医学中心种植科完成单颗后牙种植体植入术后3个月,转修复科修复的患者268例,戴入了在二氧化锆全冠中央开孔并与基台口外粘接的改良粘接固位种植修复体。修复体调整至合适后,按照各厂家要求的扭矩旋紧基台中央螺丝。分别观察基台中央螺丝初次旋紧10 min及1个月后,当扭矩扳手再次旋紧基台中央螺丝至厂家要求的扭矩时,扭矩扳手自旋转起点至终点顺时针旋转的角度。旋转的角度越大,说明基台中央螺丝扭矩丧失的情况越严重。结果:基台中央螺丝初次旋紧10 min后再次旋紧时,所有实验组病例扭矩扳手旋转的角度均为0°。基台中央螺丝初次旋紧1个月后再次旋紧时,无论实验组(基台中央螺丝初次旋紧10 min后曾再次旋紧)还是对照组(基台中央螺丝初次旋紧10 min后未再次旋紧),无论前磨牙组还是磨牙组,无论种植体是Ankylos、Straumann、Zimmer或Nobel,所有病例扭矩扳手旋转角度均>0°。其中,共有29例病例(10.82%)扭矩扳手旋转的角度>90°,且这一比例在各组间没有显著差异(P>0.05)。没有病例扭矩扳手旋转的角度达到或超过180°。结论:在部分种植系统中,单颗后牙种植修复后1个月,部分病例基台中央螺丝扭矩丧失的情况较为明显,且比例与是否曾在基台中央螺丝初次旋紧10 min后再次加力,及前磨牙或磨牙位点、采用何种植系统无关。

双开窗减压治疗中央宽基底型腰椎间盘突出钙化58例

中央型腰间盘突出钙化在腰椎间盘突出症患者中所占比例并不少,国内常采用全椎板切除、摘除钙化的椎间盘及广泛后部切除,可导致腰椎不稳或腰椎滑脱等.笔者于1998年2月-2004年8月,采用双侧椎板开窗有限扩大减压治疗中央宽基底型椎间盘钙化58例,均获较好的效果.

Study on the Flow Field around Two Parallel Moving Bubbles and Interaction Between Bubbles Rising in CMC Solutions by PIV

The flow fields surrounding two parallel moving bubbles rising from two identical orifices submerged in non-Newtonian fluid of carboxymethylcellulose （CMC） solution of three different mass concentration were measured experimentally by the use of particle image velocimetry （PIV）. The influences of gas flowrate, solution mass concentration, orifice interval and the angle between two bubble centers line and vertical direction on the flow field surrounding bubbles were discussed respectively by analyzing the velocity vector, velocity contours as well as individual velocity components. The results show that the liquid velocity both in front of two bubbles and behind increases with gas flowrate duo to shear-thinning effect of previous bubbles, whereas decreases with the increase of CMC concentration due to the increase of drag force acting on bubbles. The effect of the orifice interval on the flow field around two moving bubbles becomes gradually obvious as the interval becomes closer. Moreover, two adjacent side-by-side bubbles repulse each other during rising, leading to the practical interval between them increased somewhat above the orifice interval. When the distance between bubbles is less than the orifice interval 10 mm, the interaction between two neighboring bubbles changed from mutual repellence to attraction with the decrease of the angle of the line of linking two bubble centers to the vertical direction.

CFD modelling and optimization of oxygen supply mode in KIVCET smelting process

The influence of oxygen supply mode on the KIVCET (a Russian acronym for flash?cyclone?oxygen?electric?smelting) process was investigated using numerical simulation. The mass rate ratio (MRR) of central oxygen to lateral oxygen of the central jet distributor (CJD) burner was defined to express the oxygen supply mode, and the KIVCET process with an MRR ranging from 0.09 to 0.39 was simulated. The results show that there are four efficient reaction regions that correspond to four CJD burners. A higher central oxygen flow improves the mixing between particles and oxygen, thus enhancing reactions and shortening the reaction regions. However, a higher dust rate is induced due to the spread of the particle columns. The optimal MRR for a KIVCET furnace with a smelting capacity of 50000 kg/h is suggested to be 0.31. In this case, the chemical reactions associated with the feed are completed with an acceptable dust rate.

行业特色高校外语“3+”培养模式创新与实践——以西安某高校高起点班为例

文章在高校人才培养多元化的趋势和大学英语改革的新背景下,以西安某行业特色型高校为例,论述了高起点本科生英语培养方案、目标及课程设置。并通过社会调查和课堂教学实践构建了一个针对高水平本科生的外语培养及教学模式,试图解决目前理工科院校大学英语课程设置不合理及教学模式单一的现象,为当前的高校的外语教育和外语改革提供一定的借鉴和参考作用。

Investment Strategy of the Temasek Holdings

Sovereign Wealth Funds （SWFs） are generally known as investment funds owned by national governments and financed by the country＇s foreign currency reserves （dollar, euro, and yen）, often through their central banks or via direct investments. The study investigated the investment strategy of the Temasek Holdings as one of the most successful SWFs which is owned by the government of Singapore. Temasek Holdings was founded in 1974 to manage part of the government＇s revenues. Present turbulent times create a big pressure on healthy investment strategy of the SWFs. But total shareholder return for Temasek since its inception in 1974 has been a healthy 17% compounded annually. The main objective of the paper is to focus on the role of the Temasek Holdings as a company managed on commercial principles with an aim to achieve long-term sustainable returns. The study also analyzed Temasek Holdings＇investment strategy. The study provides answers to questions like： why Temasek is of the most successful SWFs and what is the fund risk management？ Another part of the paper compares investment strategy of the Temasek Holdings with other SWFs. The study has been conducted mainly on the basis of literature survey, secondary information and with using various web sites and research paper. The analysis has been also based on disclosures appearing in the Temasek annual reports over the period from 2008 to 2010.

HOMOLOGICAL PROPERTIES OF TORSION CLASSES UNDER CHANGE OF RINGS

Let R be a ring with identity, x be a central element of R which is neither a unit nor azero divisor. S=R/xR is the quotient ring of R and R → R/xR is the natural map.R-Mod(resp. S-Mod) denotes the category of unital left R-modules(resp. S-modules). In.this paper, relationships betwee torsion theories on R-Mod and torsion theories on S-Mod areinvestigated. Properties of the functor ExtR(N, -) are given. Properties of the localizationfunctor Qσare also investigated.

Reputation-based linear cooperation for spectrum sensing in cognitive radio networks

We propose a reputation-based cooperative spectrum sensing scheme in cognitive radio (CR) networks to solve the uncertainty resulting from the multipath fading and shadowing effect. In the proposed scheme, each cooperative CR user has a reputation degree that is initialized and adjusted by the central controller, and used to weight the sensing result from the corresponding CR user in the linear fusion process at the central controller. A simple method for adjusting the reputation degree of CR users is also presented. We analyzed and evaluated the detection performance of the reputation-based cooperative spectrum sensing scheme. Simulation results showed that our proposed scheme alleviates the problem of corrupted detection resulting from destructive channel conditions between the primary transmitter and the CR user. The performance of our proposed scheme was improved compared to the average-based linear cooperation scheme, and was similar to that of the optimal linear cooperation scheme with feasible computational complexity. Moreover, our proposed scheme does not require knowledge of channel statistics.