Efficient Phrase-Based Document Similarity for Clustering

In this paper, we propose a phrase-based document similarity to compute the pair-wise similarities of documents based on the Suffix Tree Document (STD) model. By mapping each node in the suffix tree of STD model into a unique feature term in the Vector Space Document (VSD) model, the phrase-based document similarity naturally inherits the term tf-idf weighting scheme in computing the document similarity with phrases. We apply the phrase-based document similarity to the group-average Hierarchical Agglomerative Clustering (HAC) algorithm and develop a new document clustering approach. Our evaluation experiments indicate that, the new clustering approach is very effective on clustering the documents of two standard document benchmark corpora OHSUMED and RCV1. The quality of the clustering results significantly surpass the results of traditional single-word textit{tf-idf} similarity measure in the same HAC algorithm, especially in large document data sets. Furthermore, by studying the property of STD model, we conclude that the feature vector of phrase terms in the STD model can be considered as an expanded feature vector of the traditional single-word terms in the VSD model. This conclusion sufficiently explains why the phrase-based document similarity works much better than the single-word tf-idf similarity measure.     

CyberWalk: a web-based distributed virtual walkthrough environment

A distributed virtual walkthrough environment allows users connected to the geometry server to walk through a specific place of interest, without having to travel physically. This place of interest may be a virtual museum, virtual library or virtual university. There are two basic approaches to distribute the virtual environment from the geometry server to the clients, complete replication and on-demand transmission. Although the on-demand transmission approach saves waiting time and optimizes network usage, many technical issues need to be addressed in order for the system to be interactive. CyberWalk is a web-based distributed virtual walkthrough system developed based on the on-demand transmission approach. It achieves the necessary performance with a multiresolution caching mechanism. First, it reduces the model transmission and rendering times by employing a progressive multiresolution modeling technique. Second, it reduces the Internet response time by providing a caching and prefetching mechanism. Third, it allows a client to continue to operate, at least partially, when the Internet is disconnected. The caching mechanism of CyberWalk tries to maintain at least a minimum resolution of the object models in order to provide at least a coarse view of the objects to the viewer. All these features allow CyberWalk to provide sufficient interactivity to the user for virtual walkthrough over the Internet environment. In this paper, we demonstrate the design and implementation of CyberWalk. We investigate the effectiveness of the multiresolution caching mechanism of CyberWalk in supporting virtual walkthrough applications in the Internet environment through numerous experiments, both on the simulation system and on the prototype system.     

Investigation of interface traps in LDD pMOST's by the DCIV method

Interface traps in submicron buried-channel LDD pMOSTs, generated under different stress conditions, are investigated by the direct-current current-voltage (DCIV) technique. Two peaks C and D in the DCIV spectrum are found corresponding to interface traps generated in the channel region and in the LDD region respectively. The new DCIV results clarify certain issues of the underlying mechanisms involved on hot-carrier degradation in LDD pMOSTs. Under channel hot-carrier stress conditions, the hot electron injection and electron trapping in the oxide occurs for all stressing gate voltage. However, the electron injection induced interface trap spatial location changes from the LDD region to the channel region when the stressing gate voltage changes from low to high     

How Relational are Construction Contracts?

For many years, the construction industry has relied on formal contracts to define and enforce the obligations and rights of contracting parties. Legal scholars have suggested that, based on their transaction characteristics, there are three different forms of contracts: classical, neoclassical, and relational. Of these, which form is more appropriate for use in construction projects? With increasing awareness of the importance of teamwork in construction, there is clear evidence of a rising trend in adopting a partnering approach to construction project delivery. For projects that seek to achieve a partnering relationship, relational contracts that value relationships, trust, and communication appear to be the appropriate form of contract. This paper discusses the application of relational contracts in construction by examining the fundamental question “How relational are construction contracts?” The degree of relationalism is assessed using a relational index comprising eight factors: cooperation, organizational culture, risk, trust, good faith, flexibility, the use of alternative dispute resolution, and contract duration. It was found that in the traditional design–bid–build form of delivery, the main contract and domestic subcontract forms are more relational than those of the nominated subcontract and the direct labor contract. The study was conducted in Hong Kong.     

CD56+ NK lymphomas: clinicopathological features and prognosis

Dosing regimen is an important determinant of both drug cost and patient compliance. This retrospective analysis evaluated dosing regimens and drug acquisition costs for 101 patients identified from medical records in a large metropolitan hospital as having hypertension and/or benign prostatic hyperplasia and receiving alpha-blocker therapy with either doxazosin or terazosin. Although once-daily administration is generally recommended for both drugs, 25 (38%) of 66 patients receiving terazosin were treated twice daily compared with 6 (17%) of 35 patients treated twice daily with doxazosin. This difference was statistically significant. The average (mean +/- SD) daily treatment cost per patient for all individuals receiving terazosin during the period of the record review was $1.68 +/- 0.60. For patients treated with doxazosin, the average was $0.96 +/- 0.65-a highly statistically significant result. If all 66 patients receiving terazosin had been converted to doxazosin at the beginning of the study, annual savings would have been $17,345.00. These results demonstrate the importance of reviewing actual dosing regimens. The fact that doxazosin could be administered to a significantly higher percentage of patients once daily rather than twice daily substantially decreased its cost relative to terazosin. A once-daily treatment regimen may also enhance patient compliance, thereby improving the chances of therapeutic success.     

Over-erase phenomenon in SONOS-type flash memory and its minimization using a hafnium oxide charge storage Layer

The over-erase phenomenon in the polysilicon-oxide-silicon nitride-oxide-silicon (SONOS) memory structure is minimized by using hafnium oxide or hafnium aluminum oxide to replace silicon nitride as the charge storage layer (the resulting structures are termed SOHOS devices, where the "H" denotes the high dielectric constant material instead of silicon nitride). Unlike SONOS devices, SOHOS structures show a reduced over-erase phenomenon and self-limiting charge storage behavior under both erase and program operations. These are attributed to the differences in band offset and the crystallinity of the charge storage layer.     

Accurate modeling of the effects of fringing area interface traps on scanning capacitance microscopy measurement

Scanning capacitance microscopy (SCM) is a dopant profile extraction tool with nanometer spatial resolution. While it is based on the high-frequency MOS capacitor theory, there are crucial second-order effects which make the extraction of dopant profile from SCM data a challenging task. Due to the small size of the SCM probe, the trapped charges in the interface traps at the oxide-silicon dioxide interface surrounding the probe significantly affect the measured SCM data through the fringing electric field created by the trapped charges. In this paper, we present numerical simulation results to investigate the nature of SCM dC/dV data in the presence of interface traps. The simulation takes into consideration the traps' response to the ac signal used to measure dC/dV as well as the fringing field of the trapped charge surrounding the probe tip. In this paper, we present an error estimation of experimental SCM dopant concentration extraction when the interface traps and fringing field are ignored. The trap distribution in a typical SCM sample is also investigated.     

MLAS: Multiple level authentication scheme for VANETs

The vehicular ad hoc network (VANET) is an emerging type of network which enables vehicles on roads to inter-communicate for driving safety. The basic idea is to allow arbitrary vehicles to broadcast ad hoc messages (e.g. traffic accidents) to other vehicles. However, this raises the concern of security and privacy. Messages should be signed and verified before they are trusted while the real identity of vehicles should not be revealed, but traceable by authorized party. Existing solutions either rely too heavily on a tamper-proof hardware device, or do not have an effective message verification scheme. In this paper, we propose a multiple level authentication scheme which still makes use of tamper-proof devices but the strong assumption that a long-term system master secret is preloaded into all tamper-proof devices is removed. Instead the master secret can be updated if needed to increase the security level. On the other hand, messages sent by vehicles are classified into two types – regular messages and urgent messages. Regular messages can be verified by neighboring vehicles by means of Hash-based Message Authentication Code (HMAC) while urgent messages can only be verified with the aid of RSUs nearby by means of a conditional privacy-preserving authentication scheme. Through extensive simulation, we show that our multiple level authentication scheme is much more efficient that those RSU-aided authentication scheme as long as the proportion of urgent messages is less than 100%. The verification delay required can be up to 110 times smaller than other protocols. Our implementation shows that batch verification may not be as efficient as expected. In case without batch verification, the verification delay required by our scheme can even be up to 173 times smaller.     

Low-frequency noise characterization of latent damage in thinoxides subjected to high-field impulse stressing

Latent damage in thin oxides, caused by high-field impulse stressing, can lead to increased trap generation in the device during the subsequent hot-carrier stressing. Monitoring of such damage is typically carried out by detecting the change in an appropriate electrical parameter of the device or by extracting the generated interface states and trapped charges. It was found that low-frequency noise measurements could provide a more sensitive alternative for characterizing the electrostatic discharge stress-induced latent damage in thin oxides