《水轮机控制工程》

华中科技大学魏守平教授的新书《水轮机控制工程》将于2005年7月由华中科技大学出版社出版。该书对现代水轮机调节系统和水轮机控制技术的基本原理、静态特性和动态特性进行了简要的分析;对水轮机数字式微机电液调速器的结构体系、控制器硬件构成及软件设计、机械液压系统和油压装置的工作原理、设计及计算、水轮机调节系统的试验及故障对策等做了详细的论证和叙述;分析了最新的、不同型式水轮机的、已经在电站成功应用的水轮机数字式微机电液调速器实例;研究了水轮机调速器与电网一次调频、二次调频及区域电网交换功率控制之间的关系和水轮机控制系统的仿真模型,给出了与水轮机调速器有关的电网负荷频率控制试验及仿真结果;该书还收录了作者从事水轮机调节系统动态分析工作的成果。该书可供从事水轮机调速器、水轮机控制技术及电网调度等方面的设计院、试验研究院、高等院校、电网公司、发电公司、水电厂、水轮机调速器生产企业、安装公司等的工程技术人员阅读和参考,也可作为水利水电工程等专业的本科生及研究生的教学参考书。该书约56万字,售价55元/本,有意订购者请与华中科技大学出版社联系,或通过E-mail:spwei@263.net与魏守平教授联系。

Medical treatment for sphincter of oddi dysfunction:Can it replace endoscopic sphincterotomy?

AIM:To report the results of a medical management of sphincter of oddi dysfunction(SOD) after an intermediate follow-up period.METHODS:A total of 59 patients with SOD(2 men and 57 women,mean age 51 years old) were included in this prospective study.After medical treatment for one year,the patients were clinically re-evaluated after an average period of 30 mo.RESULTS:The distribution of the patients according to the Milwaukee's classification was the following:11 patients were type 1,34 were type 2 and 14 were type 3.Fourteen patients underwent an endoscopic sphincterotomy(ES) after one year of medical treatment.The median intermediate follow-up period was 29.8 ± 3 mo(3-72 mo).The initial effectiveness of the medical treatment was complete,partial and poor among 50.8%,13.5% and 35%,respectively,of the patients.At the end of the follow-up period,37 patients(62.7%) showed more than 50% improvement.The rate of improvement in patients who required ES was not significantly different compared with the patients treated conservatively(64.2% vs 62.2%,respectively).CONCLUSION:Our study confirms that conservative medical treatment could be an alternative to endoscopic sphincterotomy because,after an intermediate follow-up period,the two treatments show the same success rates.

Parametric analysis of thermal effect on hydrostatic slipper bearing capacity of axial piston pump

Hydrostatic slipper was often used in friction bearing design, allowing improvement of the latter's dynamic behavior. The influence of thermal effect on hydrostatic slipper bearing capacity of axial piston pump was investigated. A set of lumped parameter mathematical models were developed based on energy conservation law of slipper/ swash plate pair. The results show that thermal equilibrium clearance due to solid thermal deformation periodically changes with shaft rotational angle. The slipper bearing capacity increases dramatically with decreasing thermal equilibrium clearance. In order to improve the slipper bearing capacity, length-to-diameter ratio of fixed damper varies from 3.5 to 8.75 and radius ratio of slipper varies from 1.5 to 2.0. In addition, the higher slipper thermal conductivity is useful to improve slipper bearing capability, but the thermal equilibrium clearance is not compromised.

Thoracoscopic internal mammary lymph nodes dissection: a staging tool for internal mammary lymph nodes in breast cancer

Objective： The aim of our study was to investigate the feasibility and safety of thoracoscopic internal mammary lymphadenectomy as a method to refine and thereby improve nodal staging in breast cancer. Methods： During the period from June 2004 to May 2007, 50 patients with operable breast cancer underwent modified radical mastectomy （MRM） or breast conserving surgery （BCS）, followed by thoracoscopic internal mammary lymphadenectomy, using 3 ports through the skin incision of the MRM or the BCS. Metal clips were used to mark precise site of lymphadenectomy. Results： of total number of 50 patients, the mean age of patients was 44 years （range, 27-60 years）. 40 （80%） had medio-central tumor, 10 （20%） had lateral tumor. 35 （70%） had clinically involved axillary nodes. 16 out of 50 patients received neo-adjuvant CTH. 44 patients underwent MRM and 6 patients underwent BCS. No intra-operative complications occurred. Atelectasis was the only postoperative complication that was encountered, which occurred in 12 cases, and was treated conservatively. The average chest drainage period was 1.2 day （range, 1-2 days）. The total number of IMN metastasis was 18 patients （36%）. The risk of IMN metastasis was higher; in younger patients （P = 0.03）, in medio-central tumors （P = 0.03）, in bigger tumors （P = 0.05）, with heavier metastasis of axillary LNs （P = 0.001）. But a correlation with the histological pattern of the lry tumor didn＇t exist （P = 1）. Knowing the IMN status helped in proper staging of patients, 7 patients showed evident stage migration after adding the IMN analysis to that of primary tumor and axillary LN. During the follow up period （the median, 22 months; range, 7 to 42 months）, no patient had pleural dissemination or port-site metastasis. Conclusion： Thoracoscopic IMN lymphadenectomy is a safe procedure, which can be done serious additional complications or cosmetic compromise. And allow proper nodal staging, which allow proper treatment planning.

Thermodynamic Equilibrium

The arguments in this paper lead to a new definition of thermodynamic equilibrium that remedies the deficiencies of the current forms. This definition relates thermodynamic equilibrium to its physical causes and accounts for all factors that determine it for all types of equilibrium. Standard definitions of thermodynamic equilibrium are incomplete. They do not take account of all factors that determine such equilibriums, discuss the impediments which may prevent them being reached or relate the properties that define equilibriums to the physical reasons that determine them when impediments are present. The laws of thermodynamics determine the requirements for equilibrium. These laws arise from the physical behaviour of the molecules in molecular systems and are consequences of the conservation of energy, the energies of molecules, statistics, Newton＇s laws of motion, and the equi-partition of energy. The standard definition of thermodynamic equilibrium correctly defines equilibrium whenever impediments are not factors. The discussion demonstrates how impediments arise, accounts for their role in defining equilibrium and how they relate to the energies of molecules at the conditions of the system. The new definition applies to all types of equilibrium.

Analyzing Heat Extraction and Sustainability of EGS with a Novel Model

We investigate the subsurface heat exchange process in EGS （enhanced geothermal systems） with a previously developed novel model. This model treats the porous heat reservoir as an equivalent porous medium of a single porosity. However, it considers local thermal non-equilibrium between solid rock matrix and fluid flowing in the factures and employs two energy conservation equations to describe heat transfer in the rock matrix and in the fractures, respectively, enabling the modeling and analyses of convective heat exchange in the heat reservoir. Another salient feature of this model is its capability of simulating the complete subsurface heat exchange process in EGS. The EGS subsurface geometry of interest physically consists of multiple domains： open channels for injection and production wells, the artificial heat reservoir, and the rocks enclosing the heat reservoir, while computationally we treat it as a single-domain of multiple sub-regions associated with different sets of characteristic properties （porosity and permeability, etc.）. This circumvents typical difficulties about matching boundary conditions between sub-domains in traditional multi-domain approaches and facilitates numerical implementation and simulation of the complete subsurface heat exchange process. This model is used to perform a comprehensive parametric study with respect to an imaginary doublet EGS. Effects of several parameters, including the permeability of heat reservoir, heat exchange coefficient in the heat reservoir, the specific area of fractures in the heat reservoir, and thermal compensation from surrounding rocks, on the heat extraction efficiency and EGS lifetime are analyzed.

The natural history of flail chest injuries

Purpose： Flail chest （FC） injuries represent a significant burden on trauma services because of its high morbidity and mortality. Current gold standard conservative management strategies for FC, are now being challenged by renewed interest in surgical rib fixation. This retrospective epidemiological study sets out to evaluate FC patients, and quantify the natural history of this injury by studying the injury patterns, epidemiology and mortality of patients sustaining FC injuries admitted to a major trauma centre （MTC）. Methods： A retrospective cohort analysis has been conducted at an MTC with full trauma service. All patients （age 〉 16 years） sustaining FC were included. Patient demographics, injury characteristics and inpatient stay information were extracted. Results： Two hundred and ninety-three patients were identified, with a mean injury severity score （ISS） of 28.9 （range 9-75）, average age of 56.1 years （range of 16-100）, and a male predominance （78%）. Road traffic accidents accounted for 45% （n = 132） of injuries, whilst 44% were fall or jump from height （n = 129）. Associated lung contusion was present in 133 patients （45%） while 76% of patients were found to have 5 or more ribs involved in the flail segment （n = 223） with 96% （n = 281 ） having a unilateral FC. Inpatient treatment was required 19.9 days （range 0-150 days） with 59% of patients （n = 173） requiring intensive care unit （ICU） level care for 8.4 days （range 1-63） with 61.8% requiring mechanical ventilation （n = 107） for 10.5 days （range 1-54）, and Z8g underwent rib fixation with rib plates （n = 23）. The mortality rate was found to be 14% （n = 42）. A non-significant trend towards improved outcomes in the conservative group was found when compared with the fixation group; ventilation days （6.94 vs 10.06, p = 0.18） intensive treatment unit （ITU） length of stay （LOS） （12.56 vs 15.53, p = 0.28） and hospital LOS （32.62 vs 35.24, p = 0.69）. Conclusion： This study has successfully described the natural history of flail chest injuries, and has found a nonsignificant trend towards better outcomes with conservative management. With the cohort and management challenges now defined, work on outcome improvement can be targeted. In addition the comnarahility of results to other studies makes collaboration with other MTCs a realistic vrovosal.

Rare horizontal transmission does not hide long-term inheritance of SINE highly conserved domains in the metazoan evolution

Transposable elements （TEs） are self-replicating, mobile DNA sequences which constitute a significant fraction of eukaryotic genomes. They are generally considered selfish DNA, as their replication and random insertion may have deleterious effects on genome functionalities, although some beneficial effects and evolutionary potential have been recognized. Short interspersed elements （SINEs） are non-autonomous TEs with a modular structure： a small RNA-related head, a body, and a long interspersed element-related tail. Despite their high turnover rate and de novo emergence, the body may retain highly conserved domains （HCDs） shared among divergent SINE families： in metazoans, at least nine HCD-SINEs have been recognized. Data mining on public molecular databases allowed the retrieval of 16 new HCD-SINE families from cnidarian, molluscs, arthropods, and vertebrates. Tracking the ancestry of HCDs on the metazoan phylogeny revealed that some of them date back to the Radiata-Bilateria split. Moreover, phylogenetic and age versus divergence analyses of the most ancient HCDs suggested that long-term vertical inheritance is the rule, with few horizontal transfer events. We suggest that the evolutionary conservation of HCDs may be linked to their potential to serve as recombination hotspots. This indirectly affects host genomes by maintaining active and diverse SINE lineages, whose insertions may impact （either positively or negatively） on the evolution of the genome.