Showing papers on "Point source published in 1996"

Coseismic Deformation From Earthquake Faulting On A Layered Spherical Earth

Abstract: SUMMARY A method for calculating the static displacement field following earthquake faulting in a layered spherical earth is presented At shallow levels, the Earth’s layering is characterized by sharp jumps in bulk and shear moduli at the Conrad discontinuity and the Moho and is therefore important to consider when evaluating crustal deformation The solution to the equations of static equilibrium is represented as a superposition of spheroidal and toroidal components that each depend on spherical harmonic degree and the moment tensor A method that has recently been applied to the problem of wave propagation on a layered spherical earth is here applied to the static deformation field By representing the point source in terms of discontinuities in the displacement-stress vector, the Green’s function for a particular source geometry is derived directly Numerical tests are presented to verify the accuracy of the method and to illustrate the effects of sphericity and layering on the calculated deformation fields The effect of sphericity is generally less than about 2 per cent (of maximum deformation) within 100 km of an earthquake source at crustal depths Comparisons between the deformation calculated on a spherical homogeneous earth and spherical layered earth show that up to 20 per cent errors would be introduced if the Earth’s layered structure were ignored The effect of layering is strongest for sources with a strong horizontal slip component

The dynamics of plume-ridge interaction: 2. Off-ridge plumes

Abstract: A variety of geophysical and geochemical evidence indicates that ascending mantle plumes can interact with ocean ridges located up to 1400 km away. I investigate the dynamics of this interaction using a simple model in which a point source with volume flux Q (analogous to a plume “stem”) releases buoyant fluid into a viscous corner flow driven by the divergence of rigid surface plates with thickness ∼(kx/U)1/2, where U is the half spreading rate. The point source is located at a distance xp from the ridge, and ridge migration is neglected. The buoyant fluid forms a thin sublithospheric layer whose thickness S(x, y) satisfies a nonlinear advection-diffusion equation describing the balance of advection by the corner flow, buoyancy-driven “self-spreading,” flow toward the ridge along the sloping base of the lithosphere, and continuous accretion into the lithosphere. Numerical solutions of this equation yield scaling laws for the lateral extent W (“waist width”) of plume material along the ridge, the fraction R of the plume flux that crosses the ridge, and the maximum value of xp beyond which interaction ceases. The sloping base of the lithosphere has only a minor (few tens of percent) influence on these quantities, which are determined principally by the balance of advection and self-spreading. An extension of the model to include plume-induced lithospheric thinning shows that this process increases the waist width by an amount of order 10%. Finally, the model provides a new explanation for the observation that plumes interact primarily with ridges that are migrating away from them, rather than toward them.

Depth sensing camera systems and methods

Abstract: This invention relates to a method and apparatus for sensing a three-dimensional (depth and illuminance) image of a scene It is based on the inverse-square law relating the incident brightness on an area illuminated by a light point source, to its distance from the point source In the preferred embodiment of the invention the scene is sequentially illuminated by more than one light point source each at a pre calibrated location in the reference coordinate system The resulting reflections from the field of-view are sensed by a stationary digital camera that maps each scene element into a corresponding image pixel, to provide a 2-dimensional brightness map that contains the photometric values of each image pixel for each specific illumination Each pixel photometric value depends on the illumination incident on the corresponding scene element which, in itself, is further determined by the element inherent Lambertian reflectance-coefficient at the illumination wavelength, the element orientation relative to the coordinate system, and the element illuminance as determined by the point source brightness and the distance separating the point source and the scene element Each brightness map is different from its sequel due to the differing point-source locations By manipulating the brightness maps the spatial location of each scene element relative to the fixed point sources is determined, thus yielding a depth-image as well as a brightness-image

Canonical model of volcano acoustics

Abstract: A full wave-theoretical model is developed for the acoustic field generated by an explosive point source embedded in a magma column that is open to the atmosphere. The Green's functions for the field in the magma and the atmosphere are derived on the basis of several simplifying assumptions concerning the geometry of the conduit, the boundary conditions, and the geoacoustic properties of the magma. A kinematic model for the acoustic signature of the explosive source is proposed, which, when combined with the Green's functions, provides full analytical expressions for the acoustic field in the magma and in the atmosphere as (complex) functions of frequency. By Fourier inversion the airborne pressure spectrum is transformed into a pressure time series. The predicted sound pulse in the atmosphere and its energy spectrum are highly dispersive, showing complicated structure that arises from the coherent addition of many normal modes of oscillation (i.e. depth and radial resonances) in the magma column. At high frequencies, for which the aperture of the vent is many wavelengths across, each mode is launched into the atmosphere as a parallel-sided beam of sound with a characteristic angle of elevation, which, through Snell's law, is determined by the speed of sound in the magma relative to that in air. At somewhat lower frequencies, the modal beams of sound undergo angular spreading due to diffraction at the edge of the vent. In the lowest-frequency regime, where the wavelength is comparable with the aperture, the airborne field shows little angular structure. A comparison between airborne acoustic data that we recorded in July 1994 at the western vent of Stromboli Volcano and the predictions of the theory, using parameters that are characteristic of Stromboli, show compelling agreement. The theoretical and observed power spectra both display the following features: (1) a concentration of energy below 20 Hz, associated with the first four longitudinal resonances; (2) radial resonances between 35 and 65 Hz; and (3) a broad minimum around 30 Hz, arising because the source lies near nulls in longitudinal modes that would otherwise be excited. The conclusion is that the airborne sound signature from an explosive volcanic event may be inverted to provide estimates of the depth and radius of the magma conduit, the depth, spectral shape and peak shock-wave pressure of the source, and the viscosity of the magma.

Measurement of stiffness coefficients of anisotropic materials from pointlike generation and detection of acoustic waves

Abstract: A scanned point source‐point receiver technique, based on laser generation and detection of acoustic waves, is used to measure the stiffness coefficients of anisotropic materials. The striking effects that anisotropy gives rise to are analyzed and, when possible, advantage is taken of them. The processing developed for recovering the coefficients is presented and applied starting with simulated or experimental signals. A silicon crystal, for which acoustic wave focusing induced by anisotropy is critically sensitive, is first studied. To provide an accurate interpretation of these waves, the two‐dimensional problem considering a line source is discussed, before analyzing the point source generation. Secondly, a manufactured composite material is characterized by means of this noncontact technique. By scanning a symmetry plane, four coefficients of the stiffness tensor are then recovered with good reliability.

Hybrid Seismic Modeling Based on Discrete-wave Number and Finite-difference Methods

Abstract: Any calculation of seismic wave propagation comprising the seismic source, the travel path, and the receiver site in a single finite-difference (FD) model requires a considerable amount of computer time and memory. Moreover, the methods currently available for including point sources in the 2D FD calculations are far-field approximations only. Therefore we have developed a new hybrid method for treating the seismic wave fields at localized 2D near-surface structures embedded in a 1D background medium, and excited by a point source. The source radiation and propagation in the background model is solved by the discrete-wave number (DW) method, while the propagation in the local 2D structure is calculated by the FD method. The coupling between the two sets of calculations is performed on a rectangular excitation box surrounding the local structure. We show the usefulness of the method in ground-motion studies where both near-field source effects and local site effects are important. Technical problems connected with the inconsistency between the 3D source radiation and the 2D FD calculation are minor for the relatively distant in-plane point explosive sources, but are more serious for the in-plane dislocation sources.

Flattening-filter-based empirical methods to parametrize the head scatter factor.

Abstract: Parametrizing the collimator scatter factor, S c (or head scatter factor), of a linear accelerator by the side of the equivalent square of the collimator setting at the isocenter does not accurately predict the change in S c when the width and length of a rectangular field are exchanged. We have studied two methods based on measurements of square fields to predict S c ’s of rectangular fields more accurately. The first method parametrizes S c by the side of the equivalent square of the flattening filter region visible from the point of calculation. The S c ’s of rectangular fields were predicted to an accuracy of 1% from measurements with square fields. The second method computes S c of rectangular configurations by integrating radiation that can reach the point of calculation from a point source at the target and a second extended source at the flattening filter. The radial distribution of the extended source at the level of the flattening filter is computed from S c of square fields measured at the isocenter. Effects of extended distance are modeled by separately performing inverse square law corrections for the two sources. This method also predicted the measured values to within 1% accuracy.

Method and apparatus for forming multi-dimensional attenuation correction data in tomography applications

Abstract: A method and apparatus for producing radioactive transmission measurements to form multi-dimensional attenuation correction data with a point source of radiation, such as required in position emission tomography applications. The point source of radiation (38), in one embodiment, is rapidly circulated through a conduit (36) that passes across each detector face under the influence of a transport fluid in, for example, an oscillatory motion to achieve a selected radiation field whereby calculation of transmission measurements within a body positioned within the tomograph scanner is achieved. When not being circulated, the radiation source is held within a shield (44). Circulation of the transport fluid, typically a hydraulic fluid is typically accomplished using a positive displacement pump (40). Position sensors (54, 56) are used to monitor the movement of the source in the conduit as well as its position within the shield. Disconnect units permit removal of the radiation source, as contained in the shield, from the system without accessing any other portions of the system.

Development of a computationally efficient, reactive subgrid-scale plume model and the impact in the northeastern United States using increasing levels of chemical detail

Abstract: A subgrid-scale plume model has been developed for a better treatment of dynamics of the emissions from concentrated emission sources in air quality models. The model is based on the Gaussian model description of the dispersion of NOx emissions from the power plants. Detailed inorganic and, if desired, organic atmospheric chemistry is included in the model. The plume model has been interfaced with the Urban and Regional Multiscale (URM) model and has been used to quantify the impact of subgrid-scale plume modeling on evolution of ozone and other species in the Northeast. Various simulations were performed in the northeastern United States where there are a large number of power plants over the domain. First, a case was chosen where only one large point source was followed using the subgrid plume model to better identify the local impacts of subgrid treatment. Two simulations were performed for this case; the first included a detailed inorganic chemistry in the plume, whereas the second included only simple NO-NO2-O3 chemistry. A second case was chosen where all point sources emitting more than 25 tons NOx per day were followed independently using the plume model to study the regionwide impact on predicted ozone. In addition to the two plume treatments used in the test above, a third was added that followed the plume chemistry using a full organic plus inorganic mechanism. In this case, the limited-NOx, detailed inorganic and detailed inorganic plus organic chemistry, are compared with the base case where the power plant emissions were injected directly into the airshed grid. Using the subgrid-scale plume model for large point sources had significant local impacts on predicted ozone concentrations, but regionwide impact was very small (less than 2%). Results from the simulation with the detailed organic chemistry found little difference than the detailed inorganic chemistry, though significant local differences were found between those and the simplified NOx chemistry or the calculation without the subgrid-scale treatment.

Three‐dimensional waves in layered media with nonparallel and curved interfaces: A theoretical approach

Abstract: A calculation method is presented for transducer‐generated three‐dimensional, transient wave fields in layered media with curved interfaces by using a separation approach in combination with integral transform methods and point source synthesis. The transducer‐specimen module is decomposed into different layers and the wave propagation is calculated separately in each layer. To simplify the boundary conditions, the existence of a thin liquid layer between two solid media is used. Using generalized ray theory it can be shown that the normal stress on the interface caused by an incident wave provides sufficient information to calculate the transmitted waves in the adjacent media. Two different functions for the point sources of the exciting element and the source function for normal stress are derived. By means of a source function for normal stress, the transmitted transient wave can be determined from the normal‐stress distribution on the interface. The method is demonstrated by two examples.

Discovery of an X-Ray Synchrotron Nebula Associated with the Radio Pulsar PSR B1853+01 in the Supernova Remnant W44

Abstract: We report the detection, using data from the Advanced Satellite for Cosmology and Astrophysics (ASCA), of a hard X-ray source in the vicinity of the radio pulsar PSR B1853+01, which is located within the supernova remnant (SNR) W44. PSR B1853+01, a 267 ms pulsar, has to date been detected only in the radio band. Previous observations at soft X-ray energies (e.g., with ROSAT HRI) have failed to detect any significant X-ray emission (pulsed or unpulsed) from the pulsar. In addition, no high-energy emission (4 keV) has been detected previously from W44. Over the 0.5-4.0 keV band, the ASCA data show soft thermal emission from W44, with a morphology very similar to that observed earlier by Einstein and ROSAT. In the high-energy band (4.0-9.5 keV), the SNR is, for the most part, invisible, although a source coincident with the position of PSR B1853+01 is evident. The observed ASCA spectra are consistent with a power-law origin (photon index ~2.3) for the X-ray emission from this source at a flux level (flux density ~0.5 μJy at 1 keV) consistent with previous upper limits. The maximum allowed size for the source is determined directly from the ASCA data (<5'), while the minimum size is derived from the nondetection of a point source in the ROSAT HRI data (30''). Timing analysis of the hard X-ray source failed to detect pulsations at the pulsar's period. Based on these lines of evidence, we conclude that the new hard source in W44 represents an X-ray synchrotron nebula associated with PSR B1853+01, rather than the beamed output of the pulsar itself. This discovery adds W44 to the small group of previously known plerionic SNRs. This nebula lies at the low end of, but is consistent with, the correlation between X-ray luminosity and pulsar spin-down energy loss found for such objects, lending further support to our interpretation.

Point source radiation in inhomogeneous anisotropic structures

Abstract: The ray formulae for the radiation from point sources in unbounded inhomogeneous isotropic as well as anisotropic media consist of two factors. The first one depends fully on the type and orientation of the source and on the parameters of the medium at the source. We call this factor the directivity function. The second factor depends on the parameters of the medium surrounding the source and this factor is the well-known geometrical spreading. The displacement vector and the radiation pattern defined as a modulus of the amplitude of the displacement vector measured on a unit sphere around the source are both proportional to the ratio of the directivity function and the geometrical spreading.

Low profile hemispherical lens antenna array on a ground plane

Abstract: An array of hemispherical dielectric lenses antenna on a ground plane for focusing radiation from an array of point sources, each point source being located adjacent to its respective hemispherical lens. Dual polarization point sources provide dual orthogonally polarized radiation patterns, including right and left hand circularly polarized radiation patterns. The entire antenna and ground plane may be rotated and the array of point sources may be moved relative to the hemispherical lenses so as to scan the antenna beam over a hemisphere.

IRAS Observations of the Outer Galaxy. I. Discrete Sources and Large-Scale (Diffuse) Emission

Abstract: The infrared emission in two fields of the outer Galaxy is analyzed using the IRAS image data. We present a census of discrete (but extended) IRAS sources, identified from the 60 μm images. This sample can be used to characterize the properties of typical star-forming regions.We distinguish class A sources (Galactic star-forming regions) from other Galactic objects on the basis of their flux density distributions. However, our class A sources have different infrared colors than other star formation groups (young stellar objects [YSOs] and ultracompact H II regions), as measured by the IRAS Point Source Catalogue. The class A colors, in particular the high 12 μm/25 μm ratio, are similar to the color sequence found by Boulanger et al. for the O-star-excited California Nebula. They are also similar to the colors measured, on IRAS image products, for larger "classical" H II regions embedded in large molecular clouds. The similar infrared colors suggest that most class A sources are larger, lower density regions that sample a variety of local radiation field strengths.The infrared colors of class A sources are also found to match the colors of normal spiral galaxies. This suggests that a close correspondence exists between the physical conditions in outer Galaxy star-forming regions and normal spiral galaxies.The discrete sources have been carefully measured on IRAS Coadd images, and detailed comparisons are made with the results from other IRAS data products, especially with the Point Source Catalog (PSC). Great care has been taken to investigate the uncertainties associated with these measurements, and these results may be useful for other studies that make use of IRAS image products.Information from these measurements is combined with larger scale IRAS images to investigate the relative contributions of different components of the outer Galaxy to the total mid- and far-infrared emission. At 60 and 100 km, the diffuse emission (i.e., infrared cirrus) dominates the emission from the discrete sources, which include all possible sites of star formation.

Effective source size, yield and beam profile from multi-layered bremsstrahlung targets

Abstract: Modern conformal radiotherapy benefits from heterogeneous dose delivery using scanned narrow bremsstrahlung beams of high energy in combination with dynamic double focused multi-leaf collimation and purging magnets. When using a purging magnet to remove electrons and positrons the target space is limited and unorthodox thin multi-layered targets are needed. A computational technique has therefore been developed to determine the forward yield and the angular distributions of the bremsstrahlung beam as well as the size and location of the effective and the virtual photon point source for arbitrary multi-layer bremsstrahlung targets. The Gaussian approximation of the diffusion equation for the electrons has been used and convolved with the bremsstrahlung production process. For electrons with arbitrary emittance impinging on targets of any multi-layer and atomic number combination, the model is well applicable, at least for energies in the range 1-100 MeV. The intrinsic bremsstrahlung photon profile has been determined accurately by deconvolving the electron multiple scattering process from thin experimental beryllium target profiles. For electron pencil beams incident on a target of high density and atomic number such as tungsten, the size of the effective photon source stays at around a tenth of a millimetre. The effective photon source for low-Z materials such as Be, C and Al is located at depths from 3-7 mm in the target, decreasing with increasing atomic number. The effective photon source at off-axis positions then moves out considerably from the central axis, which should be considered when aligning collimators. For high-Z materials such as tungsten, the location of the effective photon source is at a few tenths of a millimetre deep. The virtual photon point source is located only a few tenths of a millimetre upstream of the effective photon source both for high- and low-Z materials. For 50 MeV electrons incident on multi-layered full range targets the radial energy fluence distributions will have a full width at half maximum (FWHM) of 80 to 100 mm at 1 m from the target. The best target composition made of two layers when the space is limited to 15 mm was found to be 9 mm-Be followed by 6 mm W. A thin beryllium target (approximately 3 mm) results in a high-intensity bremsstrahlung lobe with a FWHM of about 35 mm at the isocentre. Interestingly, the forward dose rate in such a beam is as high as 62% of the maximum achievable with an optimal target design, even if on average only 1 MeV is lost by the electrons.

Evaluation of Monte Carlo simulation of photon counting efficiency for germanium detectors.

Abstract: The reliability of calculating the full-energy peak counting efficiency of germanium detectors by Monte Carlo simulation was evaluated by comparing MCNP-4 code results with measurements over a range of conditions. The measurements were performed for two detectors of 20% and 110% nominal efficiencies with a point source at two distances and with four different volume sources, including a reentrant beaker, placed on the end caps. The radionuclides were National Institute of Standards and Technology standard sources that emit photons between energies of 42.8 and 1,596.4 keV. Each detector was modeled in detail with respect to the dimensions of the detection volume and attenuation material in the can, dead layer, and crystal holder foil. The measurements of the 42.8-keV photon were used to check dimensions and to change slightly the value of the dead-layer thickness so that the simulation agreed with measurements at this energy. After this adjustment, the average ratio of simulation results to measurements for 13 photon energies above 42.8 keV was between 0.97 and 1.03 for all sets of point and volume source comparisons. Ratios at individual energies were between 0.92 and 1.06 for the point source and between 0.94 and 1.09 for volume sources. The observed differences were consistent with the estimated standard deviations of simulation and of measurement, which ranged from 1 to 6% and typically were 2 to 3% except for larger uncertainties at low energies. On the basis of this comparison, simulation with the MCNP-4 code is equivalent to measurement with photon standards if the detector and source configuration can be modeled within a tenth of a millimeter.

Nonlinear interaction of wave trains in a supersonic boundary layer

Abstract: Nonlinear interaction of disturbances caused by a harmonic point source in supersonic boundary layer over a flat plate is considered. It is assumed that wave lengths are much less than a characteristic scale of nonlinear interaction and the averaging technique on the intermediate scales may be used. The wave trains are considered as sums of narrow wave packets. The parameters of flow and harmonic point source are chosen in accordance with the experiments carried out by Kosinov et al. [Nonlinear Instability of Nonparallel Flows (Springer, New York, 1994)].

Seismic radiation from explosively loaded cavities in isotropic and transversely isotropic media

Abstract: We analyze the influence of cavity shape on far-field seismic-wave radiation from small explosion sources in isotropic and transversely isotropic media using the indirect boundary-element method (BEM). The analysis utilizes two possible mathematical models for the pressure fields generated by the explosion in the acoustic medium inside the cavity. One simple model for the source is a volume injection (explosion) point source inside the cavity, which generates a pressure field that arrives approximately instantaneously at each point on the cavity wall. The amplitude of the field decays at a rate inversely proportional to propagation distance. We use this model to compare results with finite-difference solutions, and the test confirms the accuracy of the BEM implementation. Strong compressional and shear signals propagate into the far-field from the source cavity, and the compressional-wave amplitude depends strongly on direction of propagation. The behavior is similar at frequencies up to 200 Hz, including those typical of regional seismic-wave propagation (1 to 10 Hz). A second model of the source, one that has been applied in previous analytical and numerical work, is to assume that the explosion will instantaneously and uniformly pressurize the source cavity. This approach yields a radiation pattern that is very different from the point source model. The compressional-wave radiation patterns have a large variation in signal strength and very strong shear waves when frequencies up to 200 Hz are included, but seismograms computed for frequency ranges of interest in regional wave propagation (around 1 Hz) have a nearly isotropic compressional-wave radiation pattern and a much smaller shear wave. This shear wave is largest for long, tunnel-like cavities or short, disklike cavities. When the cavity is located in a transversely isotropic medium, quasi-shear waves are generated, but, for the media we consider, their magnitude decreases for long, tunnel-like cavities and is larger for more equidimensional cavities. These somewhat counterintuitive results show that anisotropy can actually cause a radiation pattern to appear more isotropic than the corresponding wave fields in an isotropic medium.

Finite-Size Gravitational Microlenses

Abstract: The finite size of a gravitational microlens may have an effect on the observed amplification of a background point source. The mechanism is occlusion of one or more of the source images by the opaque bulk material of the lens as it travels in front of the source. To observe this phenomenon where both amplification and occlusion are important, the lensing geometry must be finely tuned so that the physical size of the lens is very near its Einstein radius. This condition makes the probability of an occlusion event extremely low; however, if such an event is detected, then the surface acceleration of the lens is constrained to within a geometrical factor related to the observer-lens distance. This information may provide a key to the identity of the lens. {copyright} {ital 1996 The American Astronomical Society.}

Line light source including fluorescent colorant

Abstract: A line light source (10) includes point light source (16) and a light distribution assembly (11) for transporting light from the point source (16). A fluorescent colorant is included in the light distribution assembly (11).

A ROSAT HRI observation of 3C 356: further evidence for a distant intracluster medium

Abstract: We report a 36-ks ROSAT HRI observation of the distant powerful radio galaxy 3C 356, which was detected in the PSpc. No point source is detected at the position of the radio galaxy at the flux expected from the PSPC observation, confirming that the PSPC source is extended. A weak extended source is detected in the HRI. We therefore rule out interpretations of the X-ray emission from this source as originating from the active nucleus, or a jet-cloud interaction. The emission observed with the PSPC most plausibly originates from the most distant intracluster medium yet detected in X-rays.

Acoustic point source scattering by a spherical elastic shell submerged beneath a free surface

Abstract: The scattering of incident acoustic plane waves by a submerged spherical elastic shell near a free surface has previously been analyzed in detail using an exact, classical separation of variables solution The problem is studied here again for cases where the incident waves are emitted from point sources at arbitrary positions in space The result demonstrates that for a nearby point source, the scattered wave field is significantly different from that due to a plane incident wave, and that when the distance from the point source to the shell is more than 20 shell radii, the backscattered echo can be closely approximated by that of a plane incident wave The scattered field due to an array of point sources can also be obtained by linear superpositions of the solution developed here

Galactic microlensing beyond the standard model

Abstract: For most of the Galactic microlensing events as well as for the analysis of the results from microlensing surveys, a simplified model of pointlike source objects (observed stars) and lens objects (matter between source and observer that causes a light deflection) is being used. Here I discuss effects beyond this approximation, using observed events as examples if they exhibit such effects, prospects of observing such effects, and the influence of these effects on the interpretation of the data. Moreover, I investigate whether ambiguities show up in modeling the observed events, how well model parameters are constrained by the observations, and what implications follow for the physical quantities of the lens system, which are lens mass, distance, and velocity as well as rotation period and semimajor axis for binary lenses. The effects discussed include light from other sources (blending), extended and binary lenses and sources, and rotation effects in the observer (Earth around Sun), the lens, and the source. Taking into account these “nonstandard” effects, I discuss fits for the Galactic microlensing events MACHO LMC 1, EROS 1, OGLE 1–7, and DUO 2. For fitting model parameters of microlensing light curves to the observed data, I discuss an efficient numerical approach that has been used for the fits presented in this dissertation. I argue that some of the observed events that are claimed as being due to point sources and lenses are better explained by source or lens binaries, which are more general models and include the pointlike objects as a limit. In particular, MACHO LMC 1 is best explained by a binary lens. Several different binary lens models are presented for OGLE 7 and DUO 2, which are all consistent with the observed data. I show that the inclusion of blending in fits for the OGLE 1–6 events yields large uncertainties for the event timescales and therefore for the lens masses. Since “nonstandard” events show different statistics than point source–point lens events, one has to be careful with the interpretation of the results of ongoing microlensing searches. Since the Galactic halo is an unknown population, it is difficult to make assumptions about statistics of binary objects. Binarity of objects makes it difficult to obtain the mass spectrum of the lens objects. Since the distance and velocity of the lens are not known in general, the lens mass cannot be determined directly. I derive the probability density of the lens mass for a given observed event from assumed mass densities and velocity distributions. The inclusion of the revolution of the Earth around the Sun, the source size, and the lens rotation each give an additional constraint on the lens distance and velocity, so that the lens mass can be determined (up to a twofold degeneracy) if at least two of these effects are observed. If the lens consists of a star and a planetary companion, the presented methods of estimating physical quantities of the lens system and determining the uncertainties of the fit parameters as well as the discussion of ambiguities of the fit parameters are a necessary prerequisite to draw the right conclusions from an observed light curve.