Visibility and aerosol measurement by diode-laser random-modulation CW lidar

Examples of diode laser (DL) random-modulation continuous wave (RM-CW) lidar measurements are reported. The ability of the measurement of the visibility, vertical aerosol profile, and the cloud ceiling height is demonstrated. Although the data shown here were all measured at night time, the daytime measurement is, of course, possible. For that purpose, accurate control of the laser frequency to the center frequency of a narrow band filter is required. Now a new system with a frequency control is under construction

Tropical timber trade policies : what impact will eco-labeling have?

About 20 percent of the total production of tropical timber is traded internationally. But for Indonesia, Malaysia, Papua New Guinea, and some countries in West-Central Africa, tropical timber trade accounts for more than 50 percent of production. Although the tropical timber trade has often been blamed for deforestation, the authors find that it contributes much less to deforestation than do poor policies for the production of tropical timber. Lack of tenure rights, short and uncertain logging concessions, low stumpage values, and inadequate monitoring of logging activities are among the major policy failures that help deplete the tropical forests. Trade policies, often identified as an instrument for enforcing environmental objectives internationally, are inefficient instruments for correcting domestic distortions, and in the case of tropical timber trade, may affect the environment perversely. Export and import restrictions ultimately depress the value of an already underpriced resource - the forest. Restrictions on log exports, for example, encourage wasteful processing of logs. Unless sound forest management policies are enforced domestically, the net effect could even be an increase in the rate of deforestation. Import restrictions may have a marginal impact, since trade accounts for less than 20 percent of production and most of the tropical timber is imported in Asia, where such restrictions currently do not exist. Even if import restrictions had a significant impact, it would be in a reduction in value of tropical logs that would make alternative uses of the forest lands more profitable - so the rate of deforestation might not be reduced. Eco-labeling's main strength is its capacity to discriminate (through market signals) in favor of timber produced under sound environmental practices. By contrast, bans and boycotts have an indiscriminate, perverse impact. But if eco-labeling is imposed unilaterally by a subset of countries, its effectiveness will be doubtful. It will lead to trade diversion and potentially perverse environmental results, not to mention an increase in GATT trade disputes. Even if eco-labeling is adopted by all importing countries, there could still be trade diversion in tropical timber products because some consumers may not prefer certified timber, given its higher price. Eco-labeling programs should be designed so that producers see them not as a nontariff barrier but as an instrument for capturing the rents associated with prevailing environmental concerns in the developed world. Consumer education is important to the success of such programs, and eco-labeling programs should be designed accordingly.Environmental Economics&Policies,Forestry,Silviculture,Forests and Forestry,Economic Theory&Research

New special curves and developable surfaces

We define new special curves in Euclidean 3-space which we call slant helices and conical geodesic curves. Those notions are generalizations of the notion of cylin­drical helices. One of the results in this paper gives a classification of special de­velopable surfaces under the condition of the existence of such a special curve as a geodesic. As a result, we consider geometric invariants of space curves. By using these invariants, we can estimate the order of contact with those special curves for general space curves. All arguments in this paper are elementary and classi­cal. However, there have been no papers which have investigated slant helices and conical geodesic curves so far as we know

The Effect of Poloidal Magnetic Field on Type I Planetary Migration: Significance of Magnetic Resonance

We study the effect of poloidal magnetic field on type I planetary migration by linear perturbation analysis in the shearing-sheet approximation and the analytic results are compared with numerical calculations. In contrast to the unmagnetized case, the basic equations that describe the wake due to the planet in the disk allow magnetic resonances at which density perturbation diverges. In order to simplify the problem, we consider the case without magneto-rotational instability. We perform two sets of analyses: two-dimensional and three-dimensional. In two-dimensional analysis, we find the generalization of the torque formula previously known in unmagnetized case. In three-dimensional calculations, we focus on the disk with very strong magnetic field and derive a new analytic formula for the torque exerted on the planet. We find that when Alfven velocity is much larger than sound speed, two-dimensional torque is suppressed and three-dimensional modes dominate, in contrast to the unmagnetized case.Comment: 33 pages, 10 figures, typos corrected, discussion added, reference added, Accepted for publication in Ap

Singularities of ruled surfaces in R3

We study singularities of ruled surfaces in JR3. The main result asserts that only cross­caps appear as singularities for generic ruled surfaces

Generic special curves

We study generic properties of cylindrical helices and Bertrand curves as applications of singularity theory for plane curves and spherical curves

Distinguishing genuine entangled two-photon-polarization states from independently generated pairs of entangled photons

A scheme to distinguish entangled two-photon-polarization states (ETP) from two independent entangled one-photon-polarization states (EOP) is proposed. Using this scheme, the experimental generation of ETP by parametric down-conversion is confirmed through the anti-correlations between three orthogonal two-photon-polarization states. The estimated fraction of ETP among the correlated photon pairs is 37% in the present experimental setup.Comment: 5 pages, 2 figure