Geotechnical Investigation Strategies for Lunar Base

Geotechnical characterization of potential lunar sites will be a critical part of the planning and design process. The strategies used to conduct a geotechnical investigation will be dictated by the specific needs of the lunar base, the unique environment of the lunar surface, and general character of the lunar soils and rocks. This paper outlines some of the types of geotechnical information that will be important and identifies some of the more promising strategies which might be used to obtain such information in the lunar environment. Some of the most important geotechnical information for planning and site development will be related to construction in the lunar soil. In addition to construction concerns, geotechnical data for foundation design (or verification of predesigned foundations) will be needed. The geotechnical site‐characterization work should include geophysical techniques, supplemented by conventional mechanical boring and testing only to the degree necessary to correlate geophysical measurements with conventional soil properties and to investigate anomalies. Equipment used for geotechnical site characterization will also serve for mineralogical exploration. Several techniques for geotechnical investigation that may provide very useful information in an expedient manner are described. Geophysical methods include seismic and electromagnetic methods, including seismic surveys that utilize surface waves. Electromagnetic methods such as ground‐penetrating radar are fast, efficient methods for mapping the subsurface, although these techniques do not measure soil characteristics that can readily be correlated with engineering properties. Seismic methods provide information that may correlate with soil strength, compressibility, and excavatability. In‐situ physical testing will likely include penetration testing for direct physical measurement of lunar soil behavior.     

A pseudojoint estimation of time delay and scale factor for M-wave analysis

A pseudojoint estimation of time scale and time delay between an unknown deterministic transient type signal and a reference signal is proposed. The method is based on the separation between the estimations of the two dependent parameters. The time autocorrelation function (TACF) preserves the time scale and is invariant with respect to the time delay between the signals. The time scale factor can, thus, be estimated independently from time delay using the TACFs of the two signals. After estimating the time scale factor, the signal can be scaled by the estimated amount. The time delay is then estimated without bias due to the time scale factor. To obtain high resolution joint estimates, the time scale factor is estimated in the scale domain from the scale transforms of the TACFs of the two signals. The proposed method has low computational cost. Moreover, the results on synthetic signals show good performance of the method with respect to the Cramér-Rao Lower Bound and the joint Maximum Likelihood Estimation. A possible application of the technique to the analysis of electromyogram (EMG) signals detected during electrically elicited contractions is also presented. In a few representative cases, it is shown that the time scale estimate reveals myoelectric manifestations of muscle fatigue and is less affected by M-wave truncation than spectral EMG attributes.     

Quality VoIP — An Engineering Challenge

Initial impressions of VoIP quality have not always been favourable. This paper discusses the issues behind delivering an 'appropriate' quality of service, specifically voice quality, by showing how design choices ultimately affect, and potentially limit, a customer's perception of VoIP quality.The paper continues by introducing new signal processing techniques that are helping to measure and optimise the performance of VoIP solutions.     

Models of Human Perception

As communications systems have increased in complexity it has become increasingly difficult to measure their performance objectively. In particular, when signals are compressed for more efficient transmission, conventional engineering metrics fail to predict the performance experienced by the end user — the customer. A new generation of objective measurement techniques is emerging based on models of human perception. Such models are potentially able to predict subjective performance for a wide range of transmission technologies. This paper introduces auditory and visual perceptual models and describes the development at BT Laboratories of models suitable for performance assessment. Early applications of the models are also described.     

Mandatory anonymous HIV-surveillance in Denmark. Experience with the new notification system

A newly implemented mandatory, anonymous HIV surveillance system in Denmark is described. The system is based on a serially numbered form that is circulated among the laboratories, the physicians, and the national surveillance unit. All laboratories doing confirmatory tests for HIV antibodies must send a report form along with any positive test result. Before forwarding the form to the physician, the laboratory is to fill in the top part of the form with its own name, the name and address of the requesting physician and the date of testing. The back copy must be send to the surveillance unit. The Danish physicians are by law mandated to fill in the form with data on the patient and then send the original to the surveillance unit. The two copies are for the patient's file and for the physicians' own centralized filing system. After a revision of the system in 1992, a response rate of 95% was obtained during the first year. An increasing number and proportion of first-time identified HIV-infections in Denmark are acquired heterosexually, many of these infections are identified among foreigners. The newly developed mandatory HIV surveillance system is based on anonymous reporting but it allows routine evaluation of the completeness of reporting as well as nonresponding physicians to be reminded of their duty to report. Also, the system allows nested studies to be carried out among selected HIV-infected subpopulations of special research interest without compromising the anonymity of the patient.     

Guidelines for Determining When to Use GKS and When to Use PHIGS

GKS, GKS-3D, and PHIGS are all approved ISO standards for the application programmer interface. How does a system analyst or programmer decide which standard to use for his application? This paper discusses the range of application requirements likely to be encountered, explores the suitability of GKS and PHIGS for satisfying these requirements, and offers guidelines to aid in the decision process.     

Automated sample exchange and tracking system for neutron research at cryogenic temperatures

An automated system for sample exchange and tracking in a cryogenic environment and under remote computer control was developed. Up to 24 sample "cans" per cycle can be inserted and retrieved in a programed sequence. A video camera acquires a unique identification marked on the sample can to provide a record of the sequence. All operations are coordinated via a LABVIEW program that can be operated locally or over a network. The samples are contained in vanadium cans of 6-10 mm in diameter and equipped with a hermetically sealed lid that interfaces with the sample handler. The system uses a closed-cycle refrigerator (CCR) for cooling. The sample was delivered to a precooling location that was at a temperature of approximately 25 K, after several minutes, it was moved onto a "landing pad" at approximately 10 K that locates the sample in the probe beam. After the sample was released onto the landing pad, the sample handler was retracted. Reading the sample identification and the exchange operation takes approximately 2 min. The time to cool the sample from ambient temperature to approximately 10 K was approximately 7 min including precooling time. The cooling time increases to approximately 12 min if precooling is not used. Small differences in cooling rate were observed between sample materials and for different sample can sizes. Filling the sample well and the sample can with low pressure helium is essential to provide heat transfer and to achieve useful cooling rates. A resistive heating coil can be used to offset the refrigeration so that temperatures up to approximately 350 K can be accessed and controlled using a proportional-integral-derivative control loop. The time for the landing pad to cool to approximately 10 K after it has been heated to approximately 240 K was approximately 20 min.     

Near-Field Effects on Array-Based Surface Wave Methods with Active Sources

Although the capabilities of engineering surface wave methods have improved in recent years due to several advances, a number of issues still require study to further improve the capabilities of modern surface wave methods. Near-field effects, which are one of these issues, have been studied for traditional surface wave methods with two receivers, and several criteria to mitigate the effects have been recommended. However, these criteria are not applicable to surface wave methods with multiple receivers. Moreover, the criteria are not quantitatively based and do not account for different types of soil profiles, which strongly influence near-field effects. A new study of near-field effects on surface wave methods with multiple receivers was conducted via numerical simulations, laboratory simulations, and field tests. Quantitatively based criteria for near-field effects in different soil profiles are presented using two normalized parameters developed in this study. There was excellent agreement between numerical and experimental results, and it was found that underestimation of measured Rayleigh phase velocities was the major symptom of near-field effects.