便携的视觉享受

对于不自己开车的旅行爱好者,与公共交通工具打交道是常事。飞机、火车、大巴、长途客车、渡轮,等等。我也是其中的一员,同时,作为一名技术编辑,我还对人们如何用小电器打发旅途时间怀有很大的兴趣。苹果的iPod和白色的招牌耳机随处可见,还有很多人无聊地玩手机铃声。在PDA屏幕     

The effects of the catalytic converter and fuel sulfur level on motor vehicle particulate matter emissions: light duty diesel vehicles

Wind tunnel measurements and direct tailpipe particulate matter (PM) sampling are utilized to examine how the combination of oxidation catalyst and fuel sulfur content affects the nature and quantity of PM emissions from the exhaust of a light duty diesel truck. When low sulfur fuel (4 ppm) is used, or when high sulfur (350 ppm)fuel is employed without an active catalyst present, a single log-normal distribution of exhaust particles is observed with a number mean diameter in the range of 70-83 nm. In the absence of the oxidation catalyst, the high sulfur level has at most a modest effect on particle emissions (<50%) and a minor effect on particle size (<5%). In combination with the active oxidation catalyst tested, high sulfur fuel can lead to a second, nanoparticle, mode, which appears at approximately 20 nm during high speed operation (70 mph), but is not present at low speed (40 mph). A thermodenuder significantly reduces the nanoparticle mode when set to temperatures above approximately 200 degrees C, suggesting that these particles are semivolatile in nature. Because they are observed only when the catalyst is present and the sulfur level is high, this mode likely originates from the nucleation of sulfates formed over the catalyst, although the composition may also include hydrocarbons.     

Epidural spinal cord stimulation for treatment of chronic pain--some predictors of success. A 15-year experience

BACKGROUND: We have used epidural spinal cord stimulation (SCS) for pain control for the past 15 years. An analysis of our series of 235 patients has clarified the value of specific prognostic parameters in the prediction of successful SCS. METHODS: Patients were followed up for periods ranging from 6 months to 15 years with a mean follow-up of 66 months. The mean age of the 150 men and 85 women in the study was 51.4 years. Indications for SCS included failed back syndrome (114 patients), peripheral vascular disease (39 patients), peripheral neuropathy (30 patients), multiple sclerosis (13 patients), reflex sympathetic dystrophy (13 patients), and other etiologies of chronic intractable pain (26 patients). RESULTS: One hundred and eighty-nine patients received permanent devices; 111 (59%) of these patients continue to receive satisfactory pain relief. Pain attributable to failed back syndrome, reflex sympathetic dystrophy, peripheral vascular disease of lower limbs, multiple sclerosis, and peripheral neuropathy responded favorably to spinal cord stimulation. In contrast, paraplegic pain, cauda equina syndrome, stump pain, phantom limb pain, and primary bone and joint disease pain did not respond as well. Cases of cauda equina injury had promising initial pain relief, but gradually declined after a few years. After long-term follow-up, 47 of the 111 successfully implanted patients were gainfully employed, compared with 22 patients before implantation. The successful patients reported improvements in daily living as well as a decrease in analgesic usage. Multipolar stimulation systems were significantly more reliable (p < 0.001) than unipolar systems. Complications included hardware malfunction, electrode displacement, infection, and tolerance. CONCLUSION: Aside from etiologies of pain syndromes as a prognostic factor, we have identified other parameters of success. In patients who have undergone previous surgical procedures, the shorter the duration of time to implantation, the greater the rate of success (p < 0.001). The diagnosis of failed back syndrome must be considered a confounding factor in our analysis. Those patients whose pain did not follow a surgical procedure had better responses to SCS than patients who had multiple surgical procedures prior to their first implant. The advent of multipolar systems has significantly improved clinical reliability over unipolar systems. Age, sex, and laterality of pain did not prove to be of significance.     

Multiple Scattering Analysis of Retinal Blood Oximetry

A recently developed instrument, the photographic eye oximeter (PEO), has been used to make extensive measurements of retinal blood oxygen saturation in rabbits. A model for the reflection of light from the ocular fundus is developed to account for the experimental results. This model is based on the multiple scattering of photons by red blood cells (rbc's) and enables three components of detected light to be distinguished, the coherently transmitted, the diffusely scattered into the detector cone, and the diffusely scattered out of the detector cone. The small diameter of these vessels, the wavelength bands selected for measurement, the large total scattering cross section, and the sharply forward peaked scattering pattern of the red blood cells causes the detected signal from the fundus to be composed primarily of light that has diffusely traversed the vessel twice, reflecting from a background layer after a first traverse. The light is attenuated by a saturation dependent molecular absorption. Equations are derived to enable the blood oxygen saturation to be calculated from photometrically measured quantities. A theoretical calibration line for the PEO is calculated and is shown to be in very good agreement with the experimental line, especially at high saturations.     

Inspection-oriented coding service based on machine learning and semantics mining

HS codes have been adopted by the majority of countries as being the basis for import and export inspection and the generation of trade statistics. Customs authorities and international traders need a HS code query tool to make their processing efficient and automatic. Since HS codes are identified at 5–7 levels of classification, then any intelligent coding service will need to combine a knowledge database, with the techniques of data mining, machine learning and semantics reasoning. In this paper, the authors propose a comprehensive solution for such a coding service. The architecture, related techniques, technical solution and implementation considerations for the proposed system have been provided. Several of the proposed functions and implementation techniques have been developed and deployed by the Shanghai International Airport Entry-Exit Inspection and Quarantine Bureau. The coding service has been published as a Web service, and has the potential to be widely used by authorities and international traders around the world. The proposed system may also be appropriate for other applications that relate to code or classification processes, such as RFID-based or product ontology based applications.     

Bioremoval of arsenic species from contaminated waters by sulphate-reducing bacteria

A mixed culture of sulphate-reducing bacteria was used to study the bioremoval of arsenic species (As(III) or As(V)) from groundwater. During growth of a mixed SRB culture adapted to 0.1 mg/L arsenic species through repeated sub-culturing, 1 mg/L of either As(III) or As(V) was reduced to 0.3 and 0.13 mg/L respectively. Sorption experiments on the precipitate produced by batch cultured sulphate-reducing bacteria (SRB-PP) indicated a removal of about 77 and 55% of As(V) and As(III) respectively under the following conditions: pH 6.9; biomass (2 g/L); 24 h contact time; initial arsenic concentration, 1 mg/L of either species. These results were compared with synthetic iron sulphide as adsorbent. The adsorption data were fitted to Langmuir and Freundlich isotherms. Energy dispersive X-ray analysis showed the SRB-PP contained elements such as sulphur, iron, calcium and phosphorus. Biosorption studies indicated that SRB cell pellets removed about 6.6% of the As(III) and 10.5% of the As(V) from water containing an initial concentration of 1 mg/L of either arsenic species after 24 h contact.