Web预取技术综述

Web预取是减少用户访问延时、提高网络服务质量的关键技术之一,近年来已成为国内外的研究热点.通过利用WWW访问的空间局部性,Web预取使缓存机制从时间局部性向空间局部性扩展.归纳了Web预取技术的分类,概括和比较了不同类别的优势和局限性,给出了预取模型的基本框架及每部分的主要功能,并对各种评价标准进行了详细介绍.同时,深入分析和探讨了现有的几种典型预取算法,系统地比较了这些算法的优缺点.最后从在线性、协作预取、动态流行度、划分用户会话和基于语义与基于路径相结合等方面指出了Web预取技术的研究方向.     

Nicotinamide Mononucleotide Protects against Retinal Dysfunction in a Murine Model of Carotid Artery Occlusion

Cardiovascular abnormality-mediated retinal ischemia causes severe visual impairment. Retinal ischemia is involved in enormous pathological processes including oxidative stress, reactive gliosis, and retinal functional deficits. Thus, maintaining retinal function by modulating those pathological processes may prevent or protect against vision loss. Over the decades, nicotinamide mononucleotide (NMN), a crucial nicotinamide adenine dinucleotide (NAD⁺) intermediate, has been nominated as a promising therapeutic target in retinal diseases. Nonetheless, a protective effect of NMN has not been examined in cardiovascular diseases-induced retinal ischemia. In our study, we aimed to investigate its promising effect of NMN in the ischemic retina of a murine model of carotid artery occlusion. After surgical unilateral common carotid artery occlusion (UCCAO) in adult male C57BL/6 mice, NMN (500 mg/kg/day) was intraperitoneally injected to mice every day until the end of experiments. Electroretinography and biomolecular assays were utilized to measure ocular functional and further molecular alterations in the retina. We found that UCCAO-induced retinal dysfunction was suppressed, pathological gliosis was reduced, retinal NAD⁺ levels were preserved, and the expression of an antioxidant molecule (nuclear factor erythroid-2-related factor 2; Nrf2) was upregulated by consecutive administration of NMN. Our present outcomes first suggest a promising NMN therapy for the suppression of cardiovascular diseases-mediated retinal ischemic dysfunction.     

焊缝熔宽动态实时检测研究

本文以通过焊接熔池中心的红外扫描横向温度场为根据,提出了一种新颖的焊缝熔宽动态实时检测装置,其检测数据可通过显示、打印系统,进行监视、记录,亦可直接送入微型计算机实现熔宽自适应控制。     

B/S模式下的社区再就业管理信息系统探讨与实践

随着Internet的广泛应用,浏览器/服务器(B/S)结构的管理信息系统以其界面友好、操作简单、维护方便等特点,越来越受到用户的青睐。本文对B/S模式下的社区再就业管理信息的开发的设计思路、系统组成、系统功能以及系统软硬件平台选择进行了详细探讨,并结合大庆市再就业工作的实际情况,进行了系统开发的实例介绍。     

Three-dimensional images of hepatic tumors and hepatic vessels obtained by helical computed tomography

Helical computed tomography was performed with intravenous contrast material administration in ten patients with hepatic tumors (metastatic tumor, n = 6; hepatocellular carcinoma, n = 4). Maximum intensity projection (MIP) images of intrahepatic portal venous branches and hepatic veins, and shaded surface display (SSD) images of the hepatic tumors were reconstructed for each patient. The MIP image and SSD image were fitted to overlap on a single display to obtain three-dimensional (3-D) images showing both the hepatic vessels and hepatic tumors. Subsegmental localization of the tumors determined from the 3-D images proved to be correct in all of the six patients who received hepatic resection after examination. 3-D images seem to be useful for preoperative assessment of hepatic tumors.     

The recent trend of coronary surgery

As the use of PTCA (Percutaneous Transluminal Coronary Angioplasty) is progressively widespread, the indication of CABG (Coronary Artery Bypass Grafting) and its candidates are changing accordingly. At present the candidates for CABG have left main trunk disease or severe triple-vessel disease, which are difficult or too dangerous to undergo PTCA. We should also note the population of operative candidates is becoming gradually older than before. The results from CABG appear to be limited according to the random follow-up studies in Europe and United States. The recurrence of angina and myocardial infarction tends to happen after five years. Our follow-up study shows the same tendency as those studies abroad. In order to improve the long-term results of CABG, we recommend the use of arterial grafts such as internal mammary artery, opt to the complete revascularization, and follow the patients postoperatively maximum medical therapy. At the same time, we should stress the importance of deciding the best operative opportunity, and not hesitate to make the decision for reoperation if it became necessary. Older candidates have tendency to suffer from neurological or respiratory complications during the postoperative period. If the risk of those complications appears great from the preoperative examination, we must make efforts to prevent those complications and finish CABG in the shortest possible time. Recently the cases for emergent CABG are decreasing for unstable angina or acute myocardial infarction, because PTCA is more effective for a short time. Time appears to be the most limiting factor for emergent coronary revascularization. Therefore the indication of emergent CABG is left only for left main trunk disease or severe triple vessel disease with complete occlusion of two coronary vessels. As a conclusion, CABG should be considered as only a palliative therapy same as PTCA and other medical treatments. Therefore the treatment of ischemic heart disease must be constituted by a integrated strategy including PTCA and drug therapy arranged for each patient.     

Morphology and microstructure of electrochemically deposited calcium phosphates in a modified simulated body fluid

Calcium phosphates were deposited on a pure titanium plate for various loading times under 1.3 and 12.9 mA/cm2 in a modified simulated body fluid at 52-92 degrees C. The plate-like crystals formed under 1.3 mA/cm2 were identified to be octacalcium phosphate (OCP) and/or carbonate-containing apatite. OCP converted to carbonate-containing apatite with the elapsing time of the loading current. The needle-like precipitates formed under 12.9 mA/cm2 were identified to be carbonate-containing apatite crystals elongated parallel to the c-axis direction. The degrees of crystallinity of the deposits formed under 1.3 mA/cm2 showed the highest value around 72 degrees C, whereas those under 12.9 mA/cm2 increased with the electrolyte temperature. The carbonate content of the deposits decreased with the electrolyte temperature and the flow current. The degree of crystallinity of the electrochemically deposited calcium phosphates decreased with the carbonate content.     

Detailed analysis of high‐quality symmetrical octagonal spiral inductors on Si substrate

Research studies of symmetrical spiral inductors for silicon technology have become very important and challenging. In this article, we attempt to give a detailed explanation of how symmetrical spiral inductors help to improve the quality factor (Q) as compared to conventional nonsymmetrical inductors. The experimental results are presented to verify our theory. © 2005 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2005.     

Rate adaptive video transmission over ad-hoc networks

A packet control mechanism via a cross-layer feedback to reduce bursts of packet drops for transmission of video over mobile multihop ad-hoc networks is presented. With this approach, the application layer would be capable of controlling the packet transmission flow in accordance with the multihop characteristics of the routing layer.